LibWeb: Add Event.timeStamp

Note that the value is always 0 for now. Actually initializing the time
stamp is left as a FIXME.

Userland/Libraries/LibWeb/DOM/Event.cpp

@@ -58,4 +58,10 @@ void Event::init_event(const String& type, bool bubbles, bool cancelable)
     initialize(type, bubbles, cancelable);
 }
 
+// https://dom.spec.whatwg.org/#dom-event-timestamp
+double Event::time_stamp() const
+{
+    return m_time_stamp;
+}
+
 }

Userland/Libraries/LibWeb/DOM/Event.h

@@ -58,6 +58,8 @@ public:
 
     virtual ~Event() { }
 
+    double time_stamp() const;
+
     const FlyString& type() const { return m_type; }
     void set_type(const StringView& type) { m_type = type; }
 
@@ -142,6 +144,8 @@ public:
 
     void init_event(const String&, bool, bool);
 
+    void set_time_stamp(double time_stamp) { m_time_stamp = time_stamp; }
+
 protected:
     explicit Event(FlyString const& type)
         : m_type(type)
@@ -183,6 +187,8 @@ private:
     Path m_path;
     TouchTargetList m_touch_target_list;
 
+    double m_time_stamp { 0 };
+
     void set_cancelled_flag();
 };
 

Userland/Libraries/LibWeb/DOM/Event.idl

@@ -21,6 +21,7 @@ interface Event {
     readonly attribute boolean composed;
 
     readonly attribute boolean isTrusted;
+    readonly attribute double timeStamp;
 
     undefined initEvent(DOMString type, optional boolean bubbles = false, optional boolean cancelable = false);