[bindings] Introduce ScriptValue.to<T> to convert to native values.

Source/bindings/core/v8/ScriptValue.h

Index: Source/bindings/core/v8/ScriptValue.h
diff --git a/Source/bindings/core/v8/ScriptValue.h b/Source/bindings/core/v8/ScriptValue.h
index ca543728397bfa153f717b246367ab07a5b15eb2..4a727dd732a30cdab4624dc4af2e5e6e06244db8 100644
--- a/Source/bindings/core/v8/ScriptValue.h
+++ b/Source/bindings/core/v8/ScriptValue.h
@@ -31,6 +31,7 @@
 #ifndef ScriptValue_h
 #define ScriptValue_h
 
+#include "bindings/core/v8/NativeValueTraits.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/SharedPersistent.h"
 #include "core/CoreExport.h"
@@ -51,6 +52,12 @@ public:
         return ScriptValue(scriptState, toV8(value, scriptState->context()->Global(), scriptState->isolate()));
     }
 
+    template<typename T>
+    inline T to(ExceptionState& exceptionState) const
+    {
+        return NativeValueTraits<T>::nativeValue(v8Value(), isolate(), exceptionState);
+    }
+
     ScriptValue() { }
 
     ScriptValue(ScriptState* scriptState, v8::Handle<v8::Value> value)