Bug 296377. Frames that use -moz-appearance may be transparent even if their background color is set, because the background color is not painted. r+sr=dbaron,a=chofmann

layout/generic/nsContainerFrame.cpp

@@ -483,12 +483,15 @@ SyncFrameViewGeometryDependentProperties(nsPresContext*  aPresContext,
   // view's contents should be repainted and not bitblt'd
   vm->SetViewBitBltEnabled(aView, !fixedBackground);
 
+  const nsStyleDisplay* display = aStyleContext->GetStyleDisplay();
   // If the frame has a solid background color, 'background-clip:border',
   // and it's a kind of frame that paints its background, and rounded borders aren't
   // clipping the background, then it's opaque.
+  // If the frame has a native theme appearance then its background
+  // color is actually not relevant.
   PRBool  viewHasTransparentContent =
     !(hasBG && !(bg->mBackgroundFlags & NS_STYLE_BG_COLOR_TRANSPARENT) &&
-      bg->mBackgroundClip == NS_STYLE_BG_CLIP_BORDER &&
+      !display->mAppearance && bg->mBackgroundClip == NS_STYLE_BG_CLIP_BORDER &&
       aFrame->CanPaintBackground() &&
       !HasNonZeroBorderRadius(aStyleContext));
 
@@ -547,9 +550,7 @@ SyncFrameViewGeometryDependentProperties(nsPresContext*  aPresContext,
   }
   // XXX we should also set widget transparency for XUL popups
 
-  const nsStyleDisplay* display = aStyleContext->GetStyleDisplay();
   nsFrameState kidState = aFrame->GetStateBits();
-  
   PRBool isBlockLevel =
     display->IsBlockLevel() || (kidState & NS_FRAME_OUT_OF_FLOW);