Bug 1419021 - Part 1: Invalidate display items when we get a size for decoded images since this can change the display items we build. r=tnikkel

This breaks rendering when we try do a sync decode paint since we might not have created the nsDisplayImage/nsDisplayBackgroundImage yet (or cached the empty size) and so we never get to the actual paint call.

layout/generic/nsImageFrame.cpp

@@ -583,6 +583,8 @@ nsImageFrame::OnSizeAvailable(imgIRequest* aRequest, imgIContainer* aImage)
     intrinsicSizeChanged = true;
   }
 
+  MarkNeedsDisplayItemRebuild();
+
   if (intrinsicSizeChanged && (mState & IMAGE_GOTINITIALREFLOW)) {
     // Now we need to reflow if we have an unconstrained size and have
     // already gotten the initial reflow

layout/style/ImageLoader.cpp

@@ -451,6 +451,20 @@ ImageLoader::OnSizeAvailable(imgIRequest* aRequest, imgIContainer* aImage)
 
   aImage->SetAnimationMode(presContext->ImageAnimationMode());
 
+  FrameSet* frameSet = nullptr;
+  if (!mRequestToFrameMap.Get(aRequest, &frameSet)) {
+    return NS_OK;
+  }
+
+  FrameSet::size_type length = frameSet->Length();
+  for (FrameSet::size_type i = 0; i < length; i++) {
+    nsIFrame* frame = frameSet->ElementAt(i);
+
+    if (frame->StyleVisibility()->IsVisible()) {
+      frame->MarkNeedsDisplayItemRebuild();
+    }
+  }
+
   return NS_OK;
 }