Bug 966397. Part 2: Don't look at ancestors of mContainerReferenceFrame when searching for a fixed-pos ancestor we belong to, since we'll change coordinate spaces. The metadata will be attached to an ancestor layer in that case. r=mattwoodrow

--HG--
extra : rebase_source : cfb56bb2111abce99cd475b9fa8c516d53621ed4

layout/base/FrameLayerBuilder.cpp

@@ -1690,6 +1690,10 @@ ContainerState::FindFixedPosFrameForLayerData(const nsIFrame* aAnimatedGeometryR
         result = f;
         break;
       }
+      if (f == mContainerReferenceFrame) {
+        // The metadata will go on an ancestor layer if necessary.
+        return nullptr;
+      }
     }
     if (!result) {
       return nullptr;