evaluateScriptInMainWorld() should check if the target context exists before evaluating a script

Source/bindings/core/v8/ScriptController.cpp

 /*
  * Copyright (C) 2008, 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Apple Inc. 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 565 matching lines @@
 
 v8::Local<v8::Value> ScriptController::evaluateScriptInMainWorld(const ScriptSourceCode& sourceCode, AccessControlStatus corsStatus, ExecuteScriptPolicy policy)
 {
     if (policy == DoNotExecuteScriptWhenScriptsDisabled && !canExecuteScripts(AboutToExecuteScript))
         return v8::Local<v8::Value>();
 
     String sourceURL = sourceCode.url();
     const String* savedSourceURL = m_sourceURL;
     m_sourceURL = &sourceURL;
 
-    ScriptState* scriptState = ScriptState::forMainWorld(m_frame);
-    if (scriptState->contextIsEmpty())
+    v8::EscapableHandleScope handleScope(m_isolate);
+    v8::Handle<v8::Context> context = toV8Context(m_frame, DOMWrapperWorld::mainWorld());
+    if (context.IsEmpty())
         return v8::Local<v8::Value>();
 
-    v8::EscapableHandleScope handleScope(scriptState->isolate());
+    ScriptState* scriptState = ScriptState::from(context);
     ScriptState::Scope scope(scriptState);
 
     RefPtr<LocalFrame> protect(m_frame);
     if (m_frame->loader().stateMachine()->isDisplayingInitialEmptyDocument())
         m_frame->loader().didAccessInitialDocument();
 
     OwnPtr<ScriptSourceCode> maybeProcessedSourceCode =  InspectorInstrumentation::preprocess(m_frame, sourceCode);
     const ScriptSourceCode& sourceCodeToCompile = maybeProcessedSourceCode ? *maybeProcessedSourceCode : sourceCode;
 
     v8::Local<v8::Value> object = executeScriptAndReturnValue(scriptState->context(), sourceCodeToCompile, corsStatus);
@@ skipping 26 matching lines @@
         resultArray->Set(i, evaluationResult);
     }
 
     if (results) {
         for (size_t i = 0; i < resultArray->Length(); ++i)
             results->append(handleScope.Escape(resultArray->Get(i)));
     }
 }
 
 } // namespace WebCore