Make Window.prototype.toString return [object Window] at all times.

Source/bindings/core/v8/custom/V8WindowCustom.cpp

Index: Source/bindings/core/v8/custom/V8WindowCustom.cpp
diff --git a/Source/bindings/core/v8/custom/V8WindowCustom.cpp b/Source/bindings/core/v8/custom/V8WindowCustom.cpp
index f2d3ecc95104851b0406ae4abc62cb7a0a550285..5af2203cbf40bc00d14d517ac9ff96c88dea094e 100644
--- a/Source/bindings/core/v8/custom/V8WindowCustom.cpp
+++ b/Source/bindings/core/v8/custom/V8WindowCustom.cpp
@@ -218,17 +218,10 @@ void V8Window::postMessageMethodCustom(const v8::FunctionCallbackInfo<v8::Value>
     exceptionState.throwIfNeeded();
 }
 
-// FIXME(fqian): returning string is cheating, and we should
-// fix this by calling toString function on the receiver.
-// However, V8 implements toString in JavaScript, which requires
-// switching context of receiver. I consider it is dangerous.
+// TODO(arv): Remove this custom method and implement Symbol.toStringTag instead.
 void V8Window::toStringMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& info)
 {
-    v8::Local<v8::Object> domWrapper = V8Window::findInstanceInPrototypeChain(info.This(), info.GetIsolate());
-    v8::Local<v8::Object> target = domWrapper.IsEmpty() ? info.This() : domWrapper;
-    v8::Local<v8::String> value;
-    if (target->ObjectProtoToString(info.GetIsolate()->GetCurrentContext()).ToLocal(&value))
-        v8SetReturnValue(info, value);
+    v8SetReturnValueString(info, "[object Window]", info.GetIsolate());
 }
 
 void V8Window::openMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& info)