bindings: Add empty checks for toV8()

Source/bindings/core/v8/ScriptController.cpp

Index: Source/bindings/core/v8/ScriptController.cpp
diff --git a/Source/bindings/core/v8/ScriptController.cpp b/Source/bindings/core/v8/ScriptController.cpp
index dac562197a9427ea5059f6d46710f4a2b87a0028..bc90fc40411315284c253f49b20c3517dd7139be 100644
--- a/Source/bindings/core/v8/ScriptController.cpp
+++ b/Source/bindings/core/v8/ScriptController.cpp
@@ -353,6 +353,8 @@ static NPObject* createScriptObject(LocalFrame* frame, v8::Isolate* isolate)
     ScriptState::Scope scope(scriptState);
     LocalDOMWindow* window = frame->localDOMWindow();
     v8::Local<v8::Value> global = toV8(window, scriptState->context()->Global(), scriptState->isolate());
+    if (global.IsEmpty())
+        return createNoScriptObject();
     ASSERT(global->IsObject());
     return npCreateV8ScriptObject(isolate, 0, v8::Local<v8::Object>::Cast(global), window);
 }
@@ -389,7 +391,7 @@ NPObject* ScriptController::createScriptObjectForPluginElement(HTMLPlugInElement
     ScriptState::Scope scope(scriptState);
     LocalDOMWindow* window = frame()->localDOMWindow();
     v8::Local<v8::Value> v8plugin = toV8(plugin, scriptState->context()->Global(), scriptState->isolate());
-    if (!v8plugin->IsObject())
+    if (v8plugin.IsEmpty() || !v8plugin->IsObject())

[haraken, 2015/04/28 04:24:59]

I think we can remove the v8plugin->IsObject() check.

[Yuki, 2015/04/28 04:47:57]

For the code reader, it's not clear that the following call to
v8::Local<v8::Object>::Cast<v8plugin) is safe without IsObject() check.

We knew the implementation details, but those who are not familiar with details
wouldn't think it's clear.  I'd +1 to keep IsObject() check.

[bashi, 2015/04/28 05:41:53]

I'd also prefer keeping IsObject() check. Let's keep this and other IsXXX()
checks.

         return createNoScriptObject();
 
     return npCreateV8ScriptObject(scriptState->isolate(), 0, v8::Local<v8::Object>::Cast(v8plugin), window);