bindings: Use Maybe APIs in toXXX() functions

Source/bindings/core/v8/ExceptionState.h

 /*
  * Copyright (C) 2013 Google 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.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 85 matching lines @@
         return true;
     }
 
     // This method clears out the exception which |this| has.
     ScriptPromise reject(ScriptState*);
 
     Context context() const { return m_context; }
     const char* propertyName() const { return m_propertyName; }
     const char* interfaceName() const { return m_interfaceName; }
 
+    v8::Isolate* isolate() const
+    {
+        ASSERT(m_isolate);
+        return m_isolate;
+    }
+
     void rethrowV8Exception(v8::Handle<v8::Value> value)
     {
         setException(value);
     }
 
 #if ENABLE(ASSERT)
     OnStackObjectChecker& onStackObjectChecker() { return m_onStackObjectChecker; }
 #endif
 
 protected:
@@ skipping 33 matching lines @@
     TrackExceptionState(): ExceptionState(ExceptionState::UnknownContext, 0, 0, v8::Handle<v8::Object>(), v8::Isolate::GetCurrent()) { }
     virtual void throwDOMException(const ExceptionCode&, const String& message) override;
     virtual void throwTypeError(const String& message = String()) override;
     virtual void throwSecurityError(const String& sanitizedMessage, const String& unsanitizedMessage = String()) override;
     virtual void throwRangeError(const String& message) override;
 };
 
 } // namespace blink
 
 #endif // ExceptionState_h