Bug 593839. Part 1: Use nsDisplayListBuilder::IsPaintingToWindow instead of gfxContext::DESTINED_FOR_SCREEN. r=tnikkel

layout/base/nsCSSRendering.cpp

@@ -2495,8 +2495,7 @@ PaintBackgroundLayer(nsPresContext* aPresContext,
       }
     }
 
-    if (aRenderingContext.ThebesContext()->GetFlags() &
-        gfxContext::FLAG_DESTINED_FOR_SCREEN) {
+    if (aFlags & nsCSSRendering::PAINTBG_TO_WINDOW) {
       // Clip background-attachment:fixed backgrounds to the viewport, if we're
       // painting to the screen. This avoids triggering tiling in common cases,
       // without affecting output since drawing is always clipped to the viewport

layout/base/nsCSSRendering.h

@@ -224,8 +224,14 @@ struct nsCSSRendering {
      */
     PAINTBG_WILL_PAINT_BORDER = 0x01,
     /**
-     * When this flag is passed, images are synchronously decoded. */
-    PAINTBG_SYNC_DECODE_IMAGES = 0x02
+     * When this flag is passed, images are synchronously decoded.
+     */
+    PAINTBG_SYNC_DECODE_IMAGES = 0x02,
+    /**
+     * When this flag is passed, painting will go to the screen so we can
+     * take advantage of the fact that it will be clipped to the viewport.
+     */
+    PAINTBG_TO_WINDOW = 0x04
   };
   static void PaintBackground(nsPresContext* aPresContext,
                               nsIRenderingContext& aRenderingContext,

layout/base/nsDisplayList.cpp

@@ -161,6 +161,9 @@ nsDisplayListBuilder::GetBackgroundPaintFlags() {
   if (mSyncDecodeImages) {
     flags |= nsCSSRendering::PAINTBG_SYNC_DECODE_IMAGES;
   }
+  if (mIsPaintingToWindow) {
+    flags |= nsCSSRendering::PAINTBG_TO_WINDOW;
+  }
   return flags;
 }
 

layout/generic/nsObjectFrame.cpp

@@ -1255,7 +1255,7 @@ nsDisplayPlugin::Paint(nsDisplayListBuilder* aBuilder,
                        nsIRenderingContext* aCtx)
 {
   nsObjectFrame* f = static_cast<nsObjectFrame*>(mFrame);
-  f->PaintPlugin(*aCtx, mVisibleRect, GetBounds(aBuilder));
+  f->PaintPlugin(aBuilder, *aCtx, mVisibleRect, GetBounds(aBuilder));
 }
 
 PRBool
@@ -1779,7 +1779,8 @@ nsObjectFrame::BuildLayer(nsDisplayListBuilder* aBuilder,
 }
 
 void
-nsObjectFrame::PaintPlugin(nsIRenderingContext& aRenderingContext,
+nsObjectFrame::PaintPlugin(nsDisplayListBuilder* aBuilder,
+                           nsIRenderingContext& aRenderingContext,
                            const nsRect& aDirtyRect, const nsRect& aPluginRect)
 {
   // Screen painting code
@@ -2014,7 +2015,7 @@ nsObjectFrame::PaintPlugin(nsIRenderingContext& aRenderingContext,
         nativeDraw.EndNativeDrawing();
       } while (nativeDraw.ShouldRenderAgain());
       nativeDraw.PaintToContext();
-    } else if (!(ctx->GetFlags() & gfxContext::FLAG_DESTINED_FOR_SCREEN)) {
+    } else if (!aBuilder->IsPaintingToWindow()) {
       // Get PrintWindow dynamically since it's not present on Win2K,
       // which we still support
       typedef BOOL (WINAPI * PrintWindowPtr)

layout/generic/nsObjectFrame.h

@@ -239,7 +239,8 @@ protected:
                                const nsRect& aDirtyRect, nsPoint aPt);
   void PrintPlugin(nsIRenderingContext& aRenderingContext,
                    const nsRect& aDirtyRect);
-  void PaintPlugin(nsIRenderingContext& aRenderingContext,
+  void PaintPlugin(nsDisplayListBuilder* aBuilder,
+                   nsIRenderingContext& aRenderingContext,
                    const nsRect& aDirtyRect, const nsRect& aPluginRect);
 
   /**