Bug 818643. Issue an NotifyRenderingChanged callback on nsDisplayItems when we invalidate anything to do with the display item. Make nsDisplayCanvasBackground override NotifyRenderingChanged to invalidate the cached background image. r=mattwoodrow

--HG--
extra : rebase_source : c28b2804d647a991f7d2cb8167fcf039c1835d75

layout/base/FrameLayerBuilder.cpp

@@ -2348,6 +2348,7 @@ ContainerState::InvalidateForLayerChange(nsDisplayItem* aItem,
             GetTranslationForThebesLayer(newThebesLayer));
       }
     }
+    aItem->NotifyRenderingChanged();
     return;
   } 
   if (!aNewLayer) {
@@ -2410,6 +2411,7 @@ ContainerState::InvalidateForLayerChange(nsDisplayItem* aItem,
 #endif
   }
   if (!combined.IsEmpty()) {
+    aItem->NotifyRenderingChanged();
     InvalidatePostTransformRegion(newThebesLayer,
         combined.ScaleToOutsidePixels(data->mXScale, data->mYScale, mAppUnitsPerDevPixel),
         GetTranslationForThebesLayer(newThebesLayer));

layout/base/nsDisplayList.h

@@ -856,6 +856,16 @@ public:
     }
   }
 
+  /**
+   * Called when the area rendered by this display item has changed (been
+   * invalidated or changed geometry) since the last paint. This includes
+   * when the display item was not rendered at all in the last paint.
+   * It does NOT get called when a display item was being rendered and no
+   * longer is, because generally that means there is no display item to
+   * call this method on.
+   */
+  virtual void NotifyRenderingChanged() {}
+
   /**
    * @param aSnap set to true if the edges of the rectangles of the opaque
    * region would be snapped to device pixels when drawing

layout/generic/nsCanvasFrame.cpp

@@ -239,7 +239,6 @@ nsDisplayCanvasBackground::Paint(nsDisplayListBuilder* aBuilder,
     BlitSurface(dest, destRect, surf);
 
     GetUnderlyingFrame()->Properties().Set(nsIFrame::CachedBackgroundImage(), surf.forget().get());
-    GetUnderlyingFrame()->AddStateBits(NS_FRAME_HAS_CACHED_BACKGROUND);
   }
 }
 

layout/generic/nsCanvasFrame.h

@@ -181,6 +181,10 @@ public:
       mBackgroundStyle->mLayers[mLayer].mAttachment == NS_STYLE_BG_ATTACHMENT_FIXED &&
       !mBackgroundStyle->mLayers[mLayer].mImage.IsEmpty();
   }
+  virtual void NotifyRenderingChanged() MOZ_OVERRIDE
+  {
+    mFrame->Properties().Delete(nsIFrame::CachedBackgroundImage());
+  }
 
   virtual void Paint(nsDisplayListBuilder* aBuilder,
                      nsRenderingContext* aCtx) MOZ_OVERRIDE;

layout/generic/nsFrame.cpp

@@ -4867,10 +4867,6 @@ static void InvalidateFrameInternal(nsIFrame *aFrame, bool aHasDisplayItem = tru
     aFrame->Properties().Delete(nsIFrame::InvalidationRect());
     aFrame->RemoveStateBits(NS_FRAME_HAS_INVALID_RECT);
   }
-  if (aFrame->HasAnyStateBits(NS_FRAME_HAS_CACHED_BACKGROUND)) {
-    aFrame->Properties().Delete(nsIFrame::CachedBackgroundImage());
-    aFrame->RemoveStateBits(NS_FRAME_HAS_CACHED_BACKGROUND);
-  }
 }
 
 void

layout/generic/nsIFrame.h

@@ -296,10 +296,6 @@ typedef uint64_t nsFrameState;
 // the frames for future reference.
 #define NS_FRAME_NO_COMPONENT_ALPHA                 NS_FRAME_STATE_BIT(45)
 
-// Frame has a cached rasterization of anV
-// nsDisplayBackground display item
-#define NS_FRAME_HAS_CACHED_BACKGROUND              NS_FRAME_STATE_BIT(46)
-
 // The frame is a descendant of nsSVGTextFrame2 and is thus used for SVG
 // text layout.
 #define NS_FRAME_IS_SVG_TEXT                        NS_FRAME_STATE_BIT(47)