Introduce KeepAliveWhilePending to ScriptPromiseResolverWithContext.

Source/bindings/v8/ScriptPromiseResolverWithContext.h

Index: Source/bindings/v8/ScriptPromiseResolverWithContext.h
diff --git a/Source/bindings/v8/ScriptPromiseResolverWithContext.h b/Source/bindings/v8/ScriptPromiseResolverWithContext.h
index 0ccf94e1c1d77195839cb79d9341d22c808fd0b2..d569326245345b021b39ef43ac4dd98c74ed3fb2 100644
--- a/Source/bindings/v8/ScriptPromiseResolverWithContext.h
+++ b/Source/bindings/v8/ScriptPromiseResolverWithContext.h
@@ -27,7 +27,7 @@ namespace WebCore {
 //    ExecutionContext state. When the ExecutionContext is suspended,
 //    resolve or reject will be delayed. When it is stopped, resolve or reject
 //    will be ignored.
-class ScriptPromiseResolverWithContext : public ActiveDOMObject, public RefCounted<ScriptPromiseResolverWithContext> {
+class ScriptPromiseResolverWithContext FINAL : public ActiveDOMObject, public RefCounted<ScriptPromiseResolverWithContext> {
     WTF_MAKE_NONCOPYABLE(ScriptPromiseResolverWithContext);
 
 public:
@@ -38,6 +38,8 @@ public:
         return resolver.release();
     }
 
+    virtual ~ScriptPromiseResolverWithContext();
+
     // Anything that can be passed to toV8Value can be passed to this function.
     template <typename T>
     void resolve(T value)
@@ -68,8 +70,19 @@ public:
     virtual void resume() OVERRIDE;
     virtual void stop() OVERRIDE;
 
-protected:
-    explicit ScriptPromiseResolverWithContext(ScriptState*);
+    // This function registers |value| to the associated Promise as a hidden
+    // property. As a result, |value| will be kept alive until one of the
+    // following events happens:
+    //  - the Promise is resolved
+    //  - the Promise is rejected
+    //  - the Promise is disposed by the GC
+    //  - this object is destructed
+    template<typename T>
+    void keepObjectWhilePending(const T& value)
+    {
+        ScriptState::Scope scope(m_scriptState.get());
+        keepObjectWhilePendingInternal(toV8Value(value));
+    }
 
 private:
     enum ResolutionState {
@@ -79,6 +92,8 @@ private:
         ResolvedOrRejected,
     };
 
+    explicit ScriptPromiseResolverWithContext(ScriptState*);
+
     template<typename T>
     v8::Handle<v8::Value> toV8Value(const T& value)
     {
@@ -105,6 +120,9 @@ private:
     void onTimerFired(Timer<ScriptPromiseResolverWithContext>*);
     void clear();
 
+    void keepObjectWhilePendingInternal(v8::Handle<v8::Value>);
+    void unregisterKeptObject();
+
     ResolutionState m_state;
     const RefPtr<ScriptState> m_scriptState;
     Timer<ScriptPromiseResolverWithContext> m_timer;