bindings: Fixes perf regression by crrev.com/646523004.

Source/bindings/core/v8/V8Binding.h

 /*
 * Copyright (C) 2009 Google Inc. All rights reserved.
 * Copyright (C) 2012 Ericsson AB. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
@@ skipping 209 matching lines @@
     if (UNLIKELY(!impl)) {
         v8SetReturnValueNull(callbackInfo);
         return;
     }
     if (DOMDataStore::setReturnValueForMainWorldNonTemplate(callbackInfo.GetReturnValue(), impl))
         return;
     v8::Handle<v8::Object> wrapper = impl->wrap(callbackInfo.Holder(), callbackInfo.GetIsolate());
     v8SetReturnValue(callbackInfo, wrapper);
 }
 
+template<typename CallbackInfo>
+inline void v8SetReturnValueForMainWorld(const CallbackInfo& callbackInfo, Node* impl)
+{
+    // Since EventTarget has [Custom=ToV8] and V8EventTarget.h defines its own
+    // v8SetReturnValue family, which are slow, we need to override them with
+    // optimized versions for Node and its subclasses. Without this overload,
+    // v8SetReturnValueForMainWorld for Node would be very slow.
+    //
+    // class hierarchy:
+    //     ScriptWrappable <-- EventTarget <--+-- Node <-- ...
+    //                                        +-- Window
+    // overloads:
+    //     v8SetReturnValueForMainWorld(ScriptWrappable*)
+    //         Optimized and very fast.
+    //     v8SetReturnValueForMainWorld(EventTarget*)
+    //         Uses custom toV8 function and slow.
+    //     v8SetReturnValueForMainWorld(Node*)
+    //         Optimized and very fast.
+    //     v8SetReturnValueForMainWorld(Window*)
+    //         Uses custom toV8 function and slow.
+    v8SetReturnValueForMainWorld(callbackInfo, ScriptWrappable::fromNode(impl));
+}
+
 template<typename CallbackInfo, typename T>
 inline void v8SetReturnValueForMainWorld(const CallbackInfo& callbackInfo, PassRefPtr<T> impl)
 {
     v8SetReturnValueForMainWorld(callbackInfo, impl.get());
 }
 
 template<typename CallbackInfo, typename T>
 inline void v8SetReturnValueForMainWorld(const CallbackInfo& callbackInfo, RawPtr<T> impl)
 {
     v8SetReturnValueForMainWorld(callbackInfo, impl.get());
@@ skipping 970 matching lines @@
 v8::Local<v8::Value> v8IteratorResult(ScriptState* scriptState, const T& value)
 {
     return v8IteratorResult(scriptState->isolate(), V8ValueTraits<T>::toV8Value(value, scriptState->context()->Global(), scriptState->isolate()));
 }
 
 typedef void (*InstallTemplateFunction)(v8::Handle<v8::FunctionTemplate>, v8::Isolate*);
 
 } // namespace blink
 
 #endif // V8Binding_h