Bug 579492: Use dev pixels for screen rect in PresShell::PaintRangePaintInfo. r=roc a=dbaron

layout/base/nsPresShell.cpp

@@ -5540,7 +5540,9 @@ PresShell::PaintRangePaintInfo(nsTArray<nsAutoPtr<RangePaintInfo> >* aItems,
 
   // if the area of the image is larger than the maximum area, scale it down
   float scale = 0.0;
-  nsIntRect rootScreenRect = GetRootFrame()->GetScreenRect();
+  nsIntRect rootScreenRect =
+    GetRootFrame()->GetScreenRectInAppUnits().ToNearestPixels(
+      pc->AppUnitsPerDevPixel());
 
   // if the image is larger in one or both directions than half the size of
   // the available screen area, scale the image down to that size.