Bug 539356 - Part 21 - BasicLayers should always retain content. r=roc

gfx/layers/basic/BasicImplData.h

@@ -64,14 +64,6 @@ public:
                            void* aCallbackData,
                            ReadbackProcessor* aReadback) {}
 
-  /**
-   * Implementations return true here if they *must* retain their
-   * layer contents.  This is true of shadowable layers with shadows,
-   * because there's no target on which to composite directly in the
-   * layer-publishing child process.
-   */
-  virtual bool MustRetainContent() { return false; }
-
   /**
    * Layers will get this call when their layer manager is destroyed, this
    * indicates they should clear resources they don't really need after their

gfx/layers/basic/BasicLayers.cpp

@@ -647,10 +647,7 @@ BasicThebesLayer::PaintThebes(gfxContext* aContext,
                           gfxASurface::CONTENT_COLOR_ALPHA;
   float opacity = GetEffectiveOpacity();
   
-  if (!BasicManager()->IsRetained() ||
-      (!canUseOpaqueSurface &&
-       (mContentFlags & CONTENT_COMPONENT_ALPHA) &&
-       !MustRetainContent())) {
+  if (!BasicManager()->IsRetained()) {
     NS_ASSERTION(readbackUpdates.IsEmpty(), "Can't do readback for non-retained layer");
 
     mValidRegion.SetEmpty();
@@ -2333,7 +2330,6 @@ public:
 
   virtual Layer* AsLayer() { return this; }
   virtual ShadowableLayer* AsShadowableLayer() { return this; }
-  virtual bool MustRetainContent() { return HasShadow(); }
 
   void SetBackBufferAndAttrs(const OptionalThebesBuffer& aBuffer,
                              const nsIntRegion& aValidRegion,

gfx/layers/basic/BasicTiledThebesLayer.h

@@ -173,9 +173,6 @@ public:
     mValidRegion.Sub(mValidRegion, mInvalidRegion);
   }
 
-  // BasicImplData
-  virtual bool MustRetainContent() { return HasShadow(); }
-
   // Shadow methods
   virtual void FillSpecificAttributes(SpecificLayerAttributes& aAttrs);
   virtual ShadowableLayer* AsShadowableLayer() { return this; }