Follow up to r177450, do not .As() an empty handle.

Source/bindings/core/v8/ScriptPromisePropertyBase.cpp

 // Copyright 2014 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.
 
 #include "config.h"
 #include "bindings/core/v8/ScriptPromisePropertyBase.h"
 
 #include "bindings/core/v8/V8Binding.h"
 #include "bindings/core/v8/V8HiddenValue.h"
 #include "core/dom/ExecutionContext.h"
@@ skipping 44 matching lines @@
     if (wrapper.IsEmpty()) {
         wrapper = holder(context->Global(), m_isolate);
         ASSERT(!wrapper.IsEmpty());
         ASSERT(V8HiddenValue::getHiddenValue(m_isolate, wrapper, resolverName()).IsEmpty());
         ASSERT(V8HiddenValue::getHiddenValue(m_isolate, wrapper, promiseName()).IsEmpty());
         m_mainWorldWrapper.set(m_isolate, wrapper);
         m_mainWorldWrapper.setWeak(&m_mainWorldWrapper, &clearHandle);
     }
     ASSERT(wrapper->CreationContext() == context);
 
-    v8::Handle<v8::Promise> promise = V8HiddenValue::getHiddenValue(m_isolate, wrapper, promiseName()).As<v8::Promise>();
-    if (!promise.IsEmpty()) {
-        // Return cached Promise
-        return ScriptPromise(scriptState, promise);
-    }
+    v8::Handle<v8::Value> cachedPromise = V8HiddenValue::getHiddenValue(m_isolate, wrapper, promiseName());
+    if (!cachedPromise.IsEmpty())
+        return ScriptPromise(scriptState, cachedPromise);
 
     // Create and cache the Promise
     v8::Handle<v8::Promise::Resolver> resolver = v8::Promise::Resolver::New(m_isolate);
-    promise = resolver->GetPromise();
+    v8::Handle<v8::Promise> promise = resolver->GetPromise();
     V8HiddenValue::setHiddenValue(m_isolate, wrapper, promiseName(), promise);
 
     switch (m_state) {
     case Pending:
         // Cache the resolver too
         V8HiddenValue::setHiddenValue(m_isolate, wrapper, resolverName(), resolver);
         break;
     case Resolved:
     case Rejected:
         resolveOrRejectInternal(resolver);
@@ skipping 62 matching lines @@
 
         SCRIPT_PROMISE_PROPERTIES(P)
 
 #undef P
     }
     ASSERT_NOT_REACHED();
     return v8::Handle<v8::String>();
 }
 
 } // namespace WebCore