Bug 1301245 - Part 1. Implement nsStyleImage::IsResolved. r=heycam

We need this new API in the following patch.

MozReview-Commit-ID: JSoCgzKWrfs

--HG--
extra : rebase_source : e7da0a990b991b1c417015a9cb4f9e2b1e98faae
extra : source : 8f02c1ea8448315f9284939823d66e67cdc5ad87

layout/style/nsStyleStruct.h

@@ -463,6 +463,9 @@ struct nsStyleImage
     NS_ASSERTION(mType == eStyleImageType_Gradient, "Data is not a gradient!");
     return mGradient;
   }
+  bool IsResolved() const {
+    return mType != eStyleImageType_Image || GetImageRequest()->IsResolved();
+  }
   const nsIAtom* GetElementId() const {
     NS_ASSERTION(mType == eStyleImageType_Element, "Data is not an element!");
     return mElementId;