LibJS+Everywhere: Allow Cell::initialize overrides to throw OOM errors

Note that as of this commit, there aren't any such throwers, and the
call site in Heap::allocate will drop exceptions on the floor. This
commit only serves to change the declaration of the overrides, make sure
they return an empty value, and to propagate OOM errors frm their base
initialize invocations.

Userland/Libraries/LibWeb/FileAPI/Blob.cpp

@@ -132,10 +132,12 @@ Blob::Blob(JS::Realm& realm, ByteBuffer byte_buffer)
 
 Blob::~Blob() = default;
 
-void Blob::initialize(JS::Realm& realm)
+JS::ThrowCompletionOr<void> Blob::initialize(JS::Realm& realm)
 {
-    Base::initialize(realm);
+    MUST_OR_THROW_OOM(Base::initialize(realm));
     set_prototype(&Bindings::ensure_web_prototype<Bindings::BlobPrototype>(realm, "Blob"));
+
+    return {};
 }
 
 // https://w3c.github.io/FileAPI/#ref-for-dom-blob-blob

Userland/Libraries/LibWeb/FileAPI/Blob.h

@@ -53,7 +53,7 @@ protected:
     Blob(JS::Realm&, ByteBuffer, DeprecatedString type);
     Blob(JS::Realm&, ByteBuffer);
 
-    virtual void initialize(JS::Realm&) override;
+    virtual JS::ThrowCompletionOr<void> initialize(JS::Realm&) override;
 
 private:
     explicit Blob(JS::Realm&);

Userland/Libraries/LibWeb/FileAPI/File.cpp

@@ -18,10 +18,12 @@ File::File(JS::Realm& realm, ByteBuffer byte_buffer, DeprecatedString file_name,
 {
 }
 
-void File::initialize(JS::Realm& realm)
+JS::ThrowCompletionOr<void> File::initialize(JS::Realm& realm)
 {
-    Base::initialize(realm);
+    MUST_OR_THROW_OOM(Base::initialize(realm));
     set_prototype(&Bindings::ensure_web_prototype<Bindings::FilePrototype>(realm, "File"));
+
+    return {};
 }
 
 File::~File() = default;

Userland/Libraries/LibWeb/FileAPI/File.h

@@ -31,7 +31,7 @@ public:
 private:
     File(JS::Realm&, ByteBuffer, DeprecatedString file_name, DeprecatedString type, i64 last_modified);
 
-    virtual void initialize(JS::Realm&) override;
+    virtual JS::ThrowCompletionOr<void> initialize(JS::Realm&) override;
 
     DeprecatedString m_name;
     i64 m_last_modified { 0 };

Userland/Libraries/LibWeb/FileAPI/FileList.cpp

@@ -24,10 +24,12 @@ FileList::FileList(JS::Realm& realm, Vector<JS::NonnullGCPtr<File>>&& files)
 
 FileList::~FileList() = default;
 
-void FileList::initialize(JS::Realm& realm)
+JS::ThrowCompletionOr<void> FileList::initialize(JS::Realm& realm)
 {
-    Base::initialize(realm);
+    MUST_OR_THROW_OOM(Base::initialize(realm));
     set_prototype(&Bindings::ensure_web_prototype<Bindings::FileListPrototype>(realm, "FileList"));
+
+    return {};
 }
 
 // https://w3c.github.io/FileAPI/#dfn-item

Userland/Libraries/LibWeb/FileAPI/FileList.h

@@ -35,7 +35,7 @@ public:
 private:
     FileList(JS::Realm&, Vector<JS::NonnullGCPtr<File>>&&);
 
-    virtual void initialize(JS::Realm&) override;
+    virtual JS::ThrowCompletionOr<void> initialize(JS::Realm&) override;
     virtual void visit_edges(Cell::Visitor&) override;
 
     Vector<JS::NonnullGCPtr<File>> m_files;