Have ScriptPromiseResolver on the Oilpan heap always.

Source/core/imagebitmap/ImageBitmapFactories.cpp

Index: Source/core/imagebitmap/ImageBitmapFactories.cpp
diff --git a/Source/core/imagebitmap/ImageBitmapFactories.cpp b/Source/core/imagebitmap/ImageBitmapFactories.cpp
index 2b9a28b64beda16089d9224a2ffae768ed9bcee7..422ab061da14c92860b5bb19173c086db082e433 100644
--- a/Source/core/imagebitmap/ImageBitmapFactories.cpp
+++ b/Source/core/imagebitmap/ImageBitmapFactories.cpp
@@ -50,7 +50,7 @@ namespace blink {
 
 static ScriptPromise fulfillImageBitmap(ScriptState* scriptState, PassRefPtrWillBeRawPtr<ImageBitmap> imageBitmap)
 {
-    RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
     ScriptPromise promise = resolver->promise();
     if (imageBitmap) {
         resolver->resolve(imageBitmap);