Add V8ObjectBuilder helper and use in modules/crypto/

Source/bindings/core/v8/V8ObjectBuilder.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8ObjectBuilder_h
+#define V8ObjectBuilder_h
+
+#include "bindings/core/v8/ToV8.h"
+#include "platform/heap/Handle.h"
+#include "wtf/text/WTFString.h"
+#include <v8.h>
+
+namespace blink {
+
+class ScriptState;
+class ScriptValue;
+
+class V8ObjectBuilder final {
+    STACK_ALLOCATED();
+public:
+    explicit V8ObjectBuilder(ScriptState*);
+
+    ScriptState* scriptState() const { return m_scriptState.get(); }
+
+    V8ObjectBuilder& add(String name, const V8ObjectBuilder&);

[vivekg, 2015/03/26 03:46:50]

nit: Can we use `const String&` here and subsequent places? 

+
+    V8ObjectBuilder& addNull(String name);
+    V8ObjectBuilder& addBoolean(String name, bool value);
+    V8ObjectBuilder& addNumber(String name, double value);
+    V8ObjectBuilder& addString(String name, String value);
+
+    template <typename T>
+    V8ObjectBuilder& add(String name, const T& value)
+    {
+        addInternal(name, v8::Local<v8::Value>(toV8(value, m_scriptState->context()->Global(), m_scriptState->isolate())));
+        return *this;
+    }
+
+    ScriptValue scriptValue() const;
+    v8::Local<v8::Object> v8Value() const { return m_object; }
+
+private:
+    void addInternal(String name, v8::Local<v8::Value>);
+
+    RefPtr<ScriptState> m_scriptState;
+    v8::Local<v8::Object> m_object;
+};
+
+} // namespace blink
+
+#endif // V8ObjectBuilder_h