LibWeb: Implement performance.{measure,clearMeasures}

Userland/Libraries/LibWeb/CMakeLists.txt

@@ -532,6 +532,7 @@ set(SOURCES
     URL/URLSearchParams.cpp
     URL/URLSearchParamsIterator.cpp
     UserTiming/PerformanceMark.cpp
+    UserTiming/PerformanceMeasure.cpp
     WebAssembly/Instance.cpp
     WebAssembly/Memory.cpp
     WebAssembly/Module.cpp

Userland/Libraries/LibWeb/Forward.h

@@ -567,6 +567,7 @@ class URLSearchParamsIterator;
 
 namespace Web::UserTiming {
 class PerformanceMark;
+class PerformanceMeasure;
 }
 
 namespace Web::WebAssembly {

Userland/Libraries/LibWeb/HTML/WindowOrWorkerGlobalScope.cpp

@@ -26,6 +26,7 @@
 #include <LibWeb/Infra/Base64.h>
 #include <LibWeb/PerformanceTimeline/EntryTypes.h>
 #include <LibWeb/UserTiming/PerformanceMark.h>
+#include <LibWeb/UserTiming/PerformanceMeasure.h>
 #include <LibWeb/WebIDL/AbstractOperations.h>
 #include <LibWeb/WebIDL/DOMException.h>
 #include <LibWeb/WebIDL/ExceptionOr.h>
@@ -36,7 +37,8 @@ WindowOrWorkerGlobalScopeMixin::~WindowOrWorkerGlobalScopeMixin() = default;
 
 // Please keep these in alphabetical order based on the entry type :^)
 #define ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES                                                                   \
-    __ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES(PerformanceTimeline::EntryTypes::mark, UserTiming::PerformanceMark)
+    __ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES(PerformanceTimeline::EntryTypes::mark, UserTiming::PerformanceMark) \
+    __ENUMERATE_SUPPORTED_PERFORMANCE_ENTRY_TYPES(PerformanceTimeline::EntryTypes::measure, UserTiming::PerformanceMeasure)
 
 JS::ThrowCompletionOr<void> WindowOrWorkerGlobalScopeMixin::initialize(JS::Realm& realm)
 {

Userland/Libraries/LibWeb/HighResolutionTime/Performance.cpp

@@ -8,8 +8,11 @@
 #include <LibWeb/DOM/Document.h>
 #include <LibWeb/DOM/Event.h>
 #include <LibWeb/DOM/EventDispatcher.h>
+#include <LibWeb/HTML/StructuredSerialize.h>
 #include <LibWeb/HTML/Window.h>
 #include <LibWeb/HighResolutionTime/Performance.h>
+#include <LibWeb/HighResolutionTime/TimeOrigin.h>
+#include <LibWeb/NavigationTiming/EntryNames.h>
 #include <LibWeb/NavigationTiming/PerformanceTiming.h>
 #include <LibWeb/PerformanceTimeline/EntryTypes.h>
 
@@ -89,6 +92,237 @@ void Performance::clear_marks(Optional<String> mark_name)
     // 3. Return undefined.
 }
 
+WebIDL::ExceptionOr<HighResolutionTime::DOMHighResTimeStamp> Performance::convert_name_to_timestamp(JS::Realm& realm, String const& name)
+{
+    auto& vm = realm.vm();
+
+    // 1. If the global object is not a Window object, throw a TypeError.
+    if (!is<HTML::Window>(realm.global_object()))
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, TRY_OR_THROW_OOM(vm, String::formatted("'{}' is an attribute in the PerformanceTiming interface and thus can only be used in a Window context", name)) };
+
+    // 2. If name is navigationStart, return 0.
+    if (name == NavigationTiming::EntryNames::navigationStart)
+        return 0.0;
+
+    auto timing_interface = timing();
+    VERIFY(timing_interface);
+
+    // 3. Let startTime be the value of navigationStart in the PerformanceTiming interface.
+    auto start_time = timing_interface->navigation_start();
+
+    // 4. Let endTime be the value of name in the PerformanceTiming interface.
+    u64 end_time { 0 };
+
+#define __ENUMERATE_NAVIGATION_TIMING_ENTRY_NAME(camel_case_name, snake_case_name) \
+    if (name == NavigationTiming::EntryNames::camel_case_name)                     \
+        end_time = timing_interface->snake_case_name();
+    ENUMERATE_NAVIGATION_TIMING_ENTRY_NAMES
+#undef __ENUMERATE_NAVIGATION_TIMING_ENTRY_NAME
+
+    // 5. If endTime is 0, throw an InvalidAccessError.
+    if (end_time == 0)
+        return WebIDL::InvalidAccessError::create(realm, DeprecatedString::formatted("The '{}' entry in the PerformanceTiming interface is equal to 0, meaning it hasn't happened yet", name));
+
+    // 6. Return result of subtracting startTime from endTime.
+    return static_cast<HighResolutionTime::DOMHighResTimeStamp>(end_time - start_time);
+}
+
+// https://w3c.github.io/user-timing/#dfn-convert-a-mark-to-a-timestamp
+WebIDL::ExceptionOr<HighResolutionTime::DOMHighResTimeStamp> Performance::convert_mark_to_timestamp(JS::Realm& realm, Variant<String, HighResolutionTime::DOMHighResTimeStamp> mark)
+{
+    if (mark.has<String>()) {
+        auto const& mark_string = mark.get<String>();
+
+        // 1. If mark is a DOMString and it has the same name as a read only attribute in the PerformanceTiming interface, let end
+        //    time be the value returned by running the convert a name to a timestamp algorithm with name set to the value of mark.
+#define __ENUMERATE_NAVIGATION_TIMING_ENTRY_NAME(name, _)  \
+    if (mark_string == NavigationTiming::EntryNames::name) \
+        return convert_name_to_timestamp(realm, mark_string);
+        ENUMERATE_NAVIGATION_TIMING_ENTRY_NAMES
+#undef __ENUMERATE_NAVIGATION_TIMING_ENTRY_NAME
+
+        // 2. Otherwise, if mark is a DOMString, let end time be the value of the startTime attribute from the most recent occurrence
+        //    of a PerformanceMark object in the performance entry buffer whose name is mark. If no matching entry is found, throw a
+        //    SyntaxError.
+        auto* window_or_worker = dynamic_cast<HTML::WindowOrWorkerGlobalScopeMixin*>(&realm.global_object());
+        VERIFY(window_or_worker);
+
+        auto& tuple = window_or_worker->relevant_performance_entry_tuple(PerformanceTimeline::EntryTypes::mark);
+        auto& performance_entry_buffer = tuple.performance_entry_buffer;
+
+        auto maybe_entry = performance_entry_buffer.last_matching([&mark_string](JS::Handle<PerformanceTimeline::PerformanceEntry> const& entry) {
+            return entry->name() == mark_string;
+        });
+
+        if (!maybe_entry.has_value())
+            return WebIDL::SyntaxError::create(realm, DeprecatedString::formatted("No PerformanceMark object with name '{}' found in the performance timeline", mark_string));
+
+        return maybe_entry.value()->start_time();
+    }
+
+    // 3. Otherwise, if mark is a DOMHighResTimeStamp:
+    auto mark_time_stamp = mark.get<HighResolutionTime::DOMHighResTimeStamp>();
+
+    // 1. If mark is negative, throw a TypeError.
+    if (mark_time_stamp < 0.0)
+        return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Cannot have negative time values in PerformanceMark"sv };
+
+    // 2. Otherwise, let end time be mark.
+    return mark_time_stamp;
+}
+
+// https://w3c.github.io/user-timing/#dom-performance-measure
+WebIDL::ExceptionOr<JS::NonnullGCPtr<UserTiming::PerformanceMeasure>> Performance::measure(String const& measure_name, Variant<String, UserTiming::PerformanceMeasureOptions> const& start_or_measure_options, Optional<String> end_mark)
+{
+    auto& realm = this->realm();
+    auto* window_or_worker = dynamic_cast<HTML::WindowOrWorkerGlobalScopeMixin*>(&realm.global_object());
+    VERIFY(window_or_worker);
+    auto& vm = this->vm();
+
+    // 1. If startOrMeasureOptions is a PerformanceMeasureOptions object and at least one of start, end, duration, and detail
+    //    are present, run the following checks:
+    auto const* start_or_measure_options_dictionary_object = start_or_measure_options.get_pointer<UserTiming::PerformanceMeasureOptions>();
+    if (start_or_measure_options_dictionary_object
+        && (start_or_measure_options_dictionary_object->start.has_value()
+            || start_or_measure_options_dictionary_object->end.has_value()
+            || start_or_measure_options_dictionary_object->duration.has_value()
+            || !start_or_measure_options_dictionary_object->detail.is_undefined())) {
+        // 1. If endMark is given, throw a TypeError.
+        if (end_mark.has_value())
+            return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "Cannot provide PerformanceMeasureOptions and endMark at the same time"sv };
+
+        // 2. If startOrMeasureOptions's start and end members are both omitted, throw a TypeError.
+        if (!start_or_measure_options_dictionary_object->start.has_value() && !start_or_measure_options_dictionary_object->end.has_value())
+            return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "PerformanceMeasureOptions must contain one or both of 'start' and 'end'"sv };
+
+        // 3. If startOrMeasureOptions's start, duration, and end members are all present, throw a TypeError.
+        if (start_or_measure_options_dictionary_object->start.has_value() && start_or_measure_options_dictionary_object->end.has_value() && start_or_measure_options_dictionary_object->duration.has_value())
+            return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, "PerformanceMeasureOptions cannot contain 'start', 'duration' and 'end' properties all at once"sv };
+    }
+
+    // 2. Compute end time as follows:
+    HighResolutionTime::DOMHighResTimeStamp end_time { 0.0 };
+
+    // 1. If endMark is given, let end time be the value returned by running the convert a mark to a timestamp algorithm passing
+    //    in endMark.
+    if (end_mark.has_value()) {
+        end_time = TRY(convert_mark_to_timestamp(realm, end_mark.value()));
+    }
+    // 2. Otherwise, if startOrMeasureOptions is a PerformanceMeasureOptions object, and if its end member is present, let end
+    //    time be the value returned by running the convert a mark to a timestamp algorithm passing in startOrMeasureOptions's end.
+    else if (start_or_measure_options_dictionary_object && start_or_measure_options_dictionary_object->end.has_value()) {
+        end_time = TRY(convert_mark_to_timestamp(realm, start_or_measure_options_dictionary_object->end.value()));
+    }
+    // 3. Otherwise, if startOrMeasureOptions is a PerformanceMeasureOptions object, and if its start and duration members are
+    //    both present:
+    else if (start_or_measure_options_dictionary_object && start_or_measure_options_dictionary_object->start.has_value() && start_or_measure_options_dictionary_object->duration.has_value()) {
+        // 1. Let start be the value returned by running the convert a mark to a timestamp algorithm passing in start.
+        auto start = TRY(convert_mark_to_timestamp(realm, start_or_measure_options_dictionary_object->start.value()));
+
+        // 2. Let duration be the value returned by running the convert a mark to a timestamp algorithm passing in duration.
+        auto duration = TRY(convert_mark_to_timestamp(realm, start_or_measure_options_dictionary_object->duration.value()));
+
+        // 3. Let end time be start plus duration.
+        end_time = start + duration;
+    }
+    // 4. Otherwise, let end time be the value that would be returned by the Performance object's now() method.
+    else {
+        // FIXME: Performance#now doesn't currently use TimeOrigin's functions, update this and Performance#now to match Performance#now's specification.
+        end_time = HighResolutionTime::unsafe_shared_current_time();
+    }
+
+    // 3. Compute start time as follows:
+    HighResolutionTime::DOMHighResTimeStamp start_time { 0.0 };
+
+    // 1. If startOrMeasureOptions is a PerformanceMeasureOptions object, and if its start member is present, let start time be
+    //    the value returned by running the convert a mark to a timestamp algorithm passing in startOrMeasureOptions's start.
+    if (start_or_measure_options_dictionary_object && start_or_measure_options_dictionary_object->start.has_value()) {
+        start_time = TRY(convert_mark_to_timestamp(realm, start_or_measure_options_dictionary_object->start.value()));
+    }
+    // 2. Otherwise, if startOrMeasureOptions is a PerformanceMeasureOptions object, and if its duration and end members are
+    //    both present:
+    else if (start_or_measure_options_dictionary_object && start_or_measure_options_dictionary_object->duration.has_value() && start_or_measure_options_dictionary_object->end.has_value()) {
+        // 1. Let duration be the value returned by running the convert a mark to a timestamp algorithm passing in duration.
+        auto duration = TRY(convert_mark_to_timestamp(realm, start_or_measure_options_dictionary_object->duration.value()));
+
+        // 2. Let end be the value returned by running the convert a mark to a timestamp algorithm passing in end.
+        auto end = TRY(convert_mark_to_timestamp(realm, start_or_measure_options_dictionary_object->end.value()));
+
+        // 3. Let start time be end minus duration.
+        start_time = end - duration;
+    }
+    // 3. Otherwise, if startOrMeasureOptions is a DOMString, let start time be the value returned by running the convert a mark
+    //    to a timestamp algorithm passing in startOrMeasureOptions.
+    else if (start_or_measure_options.has<String>()) {
+        start_time = TRY(convert_mark_to_timestamp(realm, start_or_measure_options.get<String>()));
+    }
+    // 4. Otherwise, let start time be 0.
+    else {
+        start_time = 0.0;
+    }
+
+    // NOTE: Step 4 (creating the entry) is done after determining values, as we set the values once during creation and never
+    //       change them after.
+
+    // 5. Set entry's name attribute to measureName.
+    // NOTE: Will be done during construction.
+
+    // 6. Set entry's entryType attribute to DOMString "measure".
+    // NOTE: Already done via the `entry_type` virtual function.
+
+    // 7. Set entry's startTime attribute to start time.
+    // NOTE: Will be done during construction.
+
+    // 8. Set entry's duration attribute to the duration from start time to end time. The resulting duration value MAY be negative.
+    auto duration = end_time - start_time;
+
+    // 9. Set entry's detail attribute as follows:
+    JS::Value detail { JS::js_null() };
+
+    // 1. If startOrMeasureOptions is a PerformanceMeasureOptions object and startOrMeasureOptions's detail member is present:
+    if (start_or_measure_options_dictionary_object && !start_or_measure_options_dictionary_object->detail.is_undefined()) {
+        // 1. Let record be the result of calling the StructuredSerialize algorithm on startOrMeasureOptions's detail.
+        auto record = TRY(HTML::structured_serialize(vm, start_or_measure_options_dictionary_object->detail));
+
+        // 2. Set entry's detail to the result of calling the StructuredDeserialize algorithm on record and the current realm.
+        detail = TRY(HTML::structured_deserialize(vm, record, realm, Optional<HTML::SerializationMemory> {}));
+    }
+
+    // 2. Otherwise, set it to null.
+    // NOTE: Already the default value of `detail`.
+
+    // 4. Create a new PerformanceMeasure object (entry) with this's relevant realm.
+    auto entry = MUST_OR_THROW_OOM(realm.heap().allocate<UserTiming::PerformanceMeasure>(realm, realm, measure_name, start_time, duration, detail));
+
+    // 10. Queue entry.
+    TRY(window_or_worker->queue_performance_entry(entry));
+
+    // 11. Add entry to the performance entry buffer.
+    // FIXME: This seems to be a holdover from moving to the `queue` structure for PerformanceObserver, as this would cause a double append.
+
+    // 12. Return entry.
+    return entry;
+}
+
+// https://w3c.github.io/user-timing/#dom-performance-clearmeasures
+void Performance::clear_measures(Optional<String> measure_name)
+{
+    auto& realm = this->realm();
+    auto* window_or_worker = dynamic_cast<HTML::WindowOrWorkerGlobalScopeMixin*>(&realm.global_object());
+    VERIFY(window_or_worker);
+
+    // 1. If measureName is omitted, remove all PerformanceMeasure objects in the performance entry buffer.
+    if (!measure_name.has_value()) {
+        window_or_worker->clear_performance_entry_buffer({}, PerformanceTimeline::EntryTypes::measure);
+        return;
+    }
+
+    // 2. Otherwise remove all PerformanceMeasure objects listed in the performance entry buffer whose name is measureName.
+    window_or_worker->remove_entries_from_performance_entry_buffer({}, PerformanceTimeline::EntryTypes::measure, measure_name.value());
+
+    // 3. Return undefined.
+}
+
 // https://www.w3.org/TR/performance-timeline/#getentries-method
 WebIDL::ExceptionOr<Vector<JS::Handle<PerformanceTimeline::PerformanceEntry>>> Performance::get_entries() const
 {

Userland/Libraries/LibWeb/HighResolutionTime/Performance.h

@@ -10,6 +10,7 @@
 #include <LibCore/ElapsedTimer.h>
 #include <LibWeb/DOM/EventTarget.h>
 #include <LibWeb/UserTiming/PerformanceMark.h>
+#include <LibWeb/UserTiming/PerformanceMeasure.h>
 
 namespace Web::HighResolutionTime {
 
@@ -26,6 +27,8 @@ public:
 
     WebIDL::ExceptionOr<JS::NonnullGCPtr<UserTiming::PerformanceMark>> mark(String const& mark_name, UserTiming::PerformanceMarkOptions const& mark_options = {});
     void clear_marks(Optional<String> mark_name);
+    WebIDL::ExceptionOr<JS::NonnullGCPtr<UserTiming::PerformanceMeasure>> measure(String const& measure_name, Variant<String, UserTiming::PerformanceMeasureOptions> const& start_or_measure_options, Optional<String> end_mark);
+    void clear_measures(Optional<String> measure_name);
 
     WebIDL::ExceptionOr<Vector<JS::Handle<PerformanceTimeline::PerformanceEntry>>> get_entries() const;
     WebIDL::ExceptionOr<Vector<JS::Handle<PerformanceTimeline::PerformanceEntry>>> get_entries_by_type(String const& type) const;
@@ -37,6 +40,9 @@ private:
     virtual JS::ThrowCompletionOr<void> initialize(JS::Realm&) override;
     virtual void visit_edges(Cell::Visitor&) override;
 
+    WebIDL::ExceptionOr<HighResolutionTime::DOMHighResTimeStamp> convert_name_to_timestamp(JS::Realm& realm, String const& name);
+    WebIDL::ExceptionOr<HighResolutionTime::DOMHighResTimeStamp> convert_mark_to_timestamp(JS::Realm& realm, Variant<String, HighResolutionTime::DOMHighResTimeStamp> mark);
+
     JS::NonnullGCPtr<HTML::Window> m_window;
     JS::GCPtr<NavigationTiming::PerformanceTiming> m_timing;
 

Userland/Libraries/LibWeb/HighResolutionTime/Performance.idl

@@ -3,6 +3,7 @@
 #import <NavigationTiming/PerformanceTiming.idl>
 #import <PerformanceTimeline/PerformanceEntry.idl>
 #import <UserTiming/PerformanceMark.idl>
+#import <UserTiming/PerformanceMeasure.idl>
 
 // https://www.w3.org/TR/performance-timeline/#dom-performanceentrylist
 typedef sequence<PerformanceEntry> PerformanceEntryList;
@@ -19,8 +20,8 @@ interface Performance : EventTarget {
     // "User Timing" extensions to the Performance interface
     PerformanceMark mark(DOMString markName, optional PerformanceMarkOptions markOptions = {});
     undefined clearMarks(optional DOMString markName);
-    // FIXME: PerformanceMeasure measure(DOMString measureName, optional (DOMString or PerformanceMeasureOptions) startOrMeasureOptions = {}, optional DOMString endMark);
-    // FIXME: undefined clearMeasures(optional DOMString measureName);
+    PerformanceMeasure measure(DOMString measureName, optional (DOMString or PerformanceMeasureOptions) startOrMeasureOptions = {}, optional DOMString endMark);
+    undefined clearMeasures(optional DOMString measureName);
 
     // https://www.w3.org/TR/performance-timeline/#extensions-to-the-performance-interface
     // "Performance Timeline" extensions to the Performance interface

Userland/Libraries/LibWeb/UserTiming/PerformanceMeasure.cpp

@@ -0,0 +1,51 @@
+/*
+ * Copyright (c) 2023, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Bindings/Intrinsics.h>
+#include <LibWeb/Bindings/PerformanceMeasurePrototype.h>
+#include <LibWeb/HTML/StructuredSerialize.h>
+#include <LibWeb/HTML/Window.h>
+#include <LibWeb/HighResolutionTime/TimeOrigin.h>
+#include <LibWeb/NavigationTiming/EntryNames.h>
+#include <LibWeb/PerformanceTimeline/EntryTypes.h>
+#include <LibWeb/UserTiming/PerformanceMeasure.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
+
+namespace Web::UserTiming {
+
+PerformanceMeasure::PerformanceMeasure(JS::Realm& realm, String const& name, HighResolutionTime::DOMHighResTimeStamp start_time, HighResolutionTime::DOMHighResTimeStamp duration, JS::Value detail)
+    : PerformanceTimeline::PerformanceEntry(realm, name, start_time, duration)
+    , m_detail(detail)
+{
+}
+
+PerformanceMeasure::~PerformanceMeasure() = default;
+
+WebIDL::ExceptionOr<JS::NonnullGCPtr<PerformanceMeasure>> PerformanceMeasure::create(JS::Realm& realm, String const& measure_name, HighResolutionTime::DOMHighResTimeStamp start_time, HighResolutionTime::DOMHighResTimeStamp duration, JS::Value detail)
+{
+    return MUST_OR_THROW_OOM(realm.heap().allocate<PerformanceMeasure>(realm, realm, measure_name, start_time, duration, detail));
+}
+
+FlyString const& PerformanceMeasure::entry_type() const
+{
+    return PerformanceTimeline::EntryTypes::measure;
+}
+
+JS::ThrowCompletionOr<void> PerformanceMeasure::initialize(JS::Realm& realm)
+{
+    MUST_OR_THROW_OOM(Base::initialize(realm));
+    set_prototype(&Bindings::ensure_web_prototype<Bindings::PerformanceMeasurePrototype>(realm, "PerformanceMeasure"));
+
+    return {};
+}
+
+void PerformanceMeasure::visit_edges(JS::Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_detail);
+}
+
+}

Userland/Libraries/LibWeb/UserTiming/PerformanceMeasure.h

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2023, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibWeb/PerformanceTimeline/PerformanceEntry.h>
+
+namespace Web::UserTiming {
+
+// https://w3c.github.io/user-timing/#dom-performancemeasureoptions
+struct PerformanceMeasureOptions {
+    JS::Value detail { JS::js_undefined() };
+    Optional<Variant<String, HighResolutionTime::DOMHighResTimeStamp>> start;
+    Optional<HighResolutionTime::DOMHighResTimeStamp> duration;
+    Optional<Variant<String, HighResolutionTime::DOMHighResTimeStamp>> end;
+};
+
+// https://w3c.github.io/user-timing/#dom-performancemeasure
+class PerformanceMeasure final : public PerformanceTimeline::PerformanceEntry {
+    WEB_PLATFORM_OBJECT(PerformanceMeasure, PerformanceTimeline::PerformanceEntry);
+
+public:
+    virtual ~PerformanceMeasure();
+
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<PerformanceMeasure>> create(JS::Realm&, String const& measure_name, HighResolutionTime::DOMHighResTimeStamp start_time, HighResolutionTime::DOMHighResTimeStamp duration, JS::Value detail);
+
+    // NOTE: These three functions are answered by the registry for the given entry type.
+    // https://w3c.github.io/timing-entrytypes-registry/#registry
+
+    // https://w3c.github.io/timing-entrytypes-registry/#dfn-availablefromtimeline
+    static PerformanceTimeline::AvailableFromTimeline available_from_timeline() { return PerformanceTimeline::AvailableFromTimeline::Yes; }
+
+    // https://w3c.github.io/timing-entrytypes-registry/#dfn-maxbuffersize
+    // NOTE: The empty state represents Infinite size.
+    static Optional<u64> max_buffer_size() { return OptionalNone {}; }
+
+    // https://w3c.github.io/timing-entrytypes-registry/#dfn-should-add-entry
+    virtual PerformanceTimeline::ShouldAddEntry should_add_entry() const override { return PerformanceTimeline::ShouldAddEntry::Yes; }
+
+    virtual FlyString const& entry_type() const override;
+
+    JS::Value detail() const { return m_detail; }
+
+private:
+    PerformanceMeasure(JS::Realm&, String const& name, HighResolutionTime::DOMHighResTimeStamp start_time, HighResolutionTime::DOMHighResTimeStamp duration, JS::Value detail);
+
+    virtual JS::ThrowCompletionOr<void> initialize(JS::Realm&) override;
+    virtual void visit_edges(JS::Cell::Visitor&) override;
+
+    // https://w3c.github.io/user-timing/#dom-performancemeasure-detail
+    JS::Value m_detail { JS::js_null() };
+};
+
+}

Userland/Libraries/LibWeb/UserTiming/PerformanceMeasure.idl

@@ -0,0 +1,13 @@
+#import <PerformanceTimeline/PerformanceEntry.idl>
+
+[Exposed=(Window,Worker), UseNewAKString]
+interface PerformanceMeasure : PerformanceEntry {
+    readonly attribute any detail;
+};
+
+dictionary PerformanceMeasureOptions {
+    any detail;
+    (DOMString or DOMHighResTimeStamp) start;
+    DOMHighResTimeStamp duration;
+    (DOMString or DOMHighResTimeStamp) end;
+};

Userland/Libraries/LibWeb/idl_files.cmake

@@ -221,6 +221,7 @@ libweb_js_bindings(UIEvents/WheelEvent)
 libweb_js_bindings(URL/URL)
 libweb_js_bindings(URL/URLSearchParams ITERABLE)
 libweb_js_bindings(UserTiming/PerformanceMark)
+libweb_js_bindings(UserTiming/PerformanceMeasure)
 libweb_js_bindings(WebAssembly/Instance)
 libweb_js_bindings(WebAssembly/Memory)
 libweb_js_bindings(WebAssembly/Module)