Have Dictionary use V8TRYCATCH_FOR_V8STRINGRESOURCE() macro

Source/bindings/v8/V8StringResource.h

Index: Source/bindings/v8/V8StringResource.h
diff --git a/Source/bindings/v8/V8StringResource.h b/Source/bindings/v8/V8StringResource.h
index 31f17813476f72edf49b0dda46d0e0fe7697995b..816e9875970bed4f6097f9ac922ab9558abc6b18 100644
--- a/Source/bindings/v8/V8StringResource.h
+++ b/Source/bindings/v8/V8StringResource.h
@@ -181,8 +181,8 @@ public:
     }
 
     bool prepare();
-    operator String() { return toString<String>(); }
-    operator AtomicString() { return toString<AtomicString>(); }
+    operator String() const { return toString<String>(); }
+    operator AtomicString() const { return toString<AtomicString>(); }
 
 private:
     bool prepareBase()
@@ -216,10 +216,10 @@ private:
     }
 
     template <class StringType>
-    StringType toString()
+    StringType toString() const
     {
         if (LIKELY(!m_v8Object.IsEmpty()))
-            return v8StringToWebCoreString<StringType>(m_v8Object.As<v8::String>(), m_mode);
+            return v8StringToWebCoreString<StringType>(const_cast<v8::Handle<v8::Value>*>(&m_v8Object)->As<v8::String>(), m_mode);
 
         return StringType(m_string);
     }