bindings: Supports serializer for PerformanceTiming.

Source/core/timing/PerformanceTiming.h

Index: Source/core/timing/PerformanceTiming.h
diff --git a/Source/core/timing/PerformanceTiming.h b/Source/core/timing/PerformanceTiming.h
index 8c0220ee0705b7bd2630a6ffc87f620dba2f1ea2..7ce38e15c7a950ddf605999267c726bcc24dcafd 100644
--- a/Source/core/timing/PerformanceTiming.h
+++ b/Source/core/timing/PerformanceTiming.h
@@ -43,6 +43,8 @@ class DocumentLoader;
 class DocumentTiming;
 class LocalFrame;
 class ResourceLoadTiming;
+class ScriptState;
+class ScriptValue;
 
 class CORE_EXPORT PerformanceTiming final : public GarbageCollectedFinalized<PerformanceTiming>, public ScriptWrappable, public DOMWindowProperty {
     DEFINE_WRAPPERTYPEINFO();
@@ -75,6 +77,8 @@ public:
     unsigned long long loadEventStart() const;
     unsigned long long loadEventEnd() const;
 
+    ScriptValue toJSONForBinding(ScriptState*);
+
     DECLARE_VIRTUAL_TRACE();
 
     unsigned long long monotonicTimeToIntegerMilliseconds(double) const;