Bug 1099298 - Revert the temporary fix in bug 1099104. r=tn

layout/base/nsDisplayList.cpp

@@ -747,15 +747,8 @@ nsDisplayScrollLayer::ComputeFrameMetrics(nsIFrame* aForFrame,
   // all the pres shells from here up to the root, as well as any css-driven
   // resolution. We don't need to compute it as it's already stored in the
   // container parameters.
-  // TODO: On Fennec, the container parameters do not appear to contain the
-  // cumulative resolution the way they do on B2G, and using them breaks
-  // rendering for normal pages (no CSS transform involves). As a temporary
-  // workaround, use the same value as the resolution-to-screen; this will make
-  // the "extra resolution" 1, and pages with CSS transforms may not be
-  // rendered correctly, but normal pages will.
-  metrics.mCumulativeResolution = LayoutDeviceToLayerScale(
-      presShell->GetCumulativeResolution().width
-    * nsLayoutUtils::GetTransformToAncestorScale(aScrollFrame ? aScrollFrame : aForFrame).width);
+  metrics.mCumulativeResolution = LayoutDeviceToLayerScale(aContainerParameters.mXScale,
+                                                           aContainerParameters.mYScale);
 
   LayoutDeviceToScreenScale resolutionToScreen(
       presShell->GetCumulativeResolution().width