Keeping track of descendants that draw content instead of recalcualting

cc/layers/picture_image_layer.cc

 // Copyright 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layers/picture_image_layer.h"
 
 #include "cc/layers/picture_image_layer_impl.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 
 namespace cc {
 
 scoped_refptr<PictureImageLayer> PictureImageLayer::Create() {
   return make_scoped_refptr(new PictureImageLayer());
 }
 
 PictureImageLayer::PictureImageLayer() : PictureLayer(this) {}
 
 PictureImageLayer::~PictureImageLayer() {
   ClearClient();
 }
 
 scoped_ptr<LayerImpl> PictureImageLayer::CreateLayerImpl(
     LayerTreeImpl* tree_impl) {
   return PictureImageLayerImpl::Create(tree_impl, id()).PassAs<LayerImpl>();
 }
 
-bool PictureImageLayer::DrawsContent() const {
-  return !bitmap_.isNull() && PictureLayer::DrawsContent();
+void PictureImageLayer::UpdateDrawsContent(bool draws_content) {
+  return PictureLayer::UpdateDrawsContent(draws_content && !bitmap_.isNull());
 }
 
 void PictureImageLayer::SetBitmap(const SkBitmap& bitmap) {
   // SetBitmap() currently gets called whenever there is any
   // style change that affects the layer even if that change doesn't
   // affect the actual contents of the image (e.g. a CSS animation).
   // With this check in place we avoid unecessary texture uploads.
   if (bitmap.pixelRef() && bitmap.pixelRef() == bitmap_.pixelRef())
     return;
 
   bitmap_ = bitmap;
+  UpdateDrawsContent(true);
   SetNeedsDisplay();
 }
 
 void PictureImageLayer::PaintContents(
     SkCanvas* canvas,
     const gfx::Rect& clip,
     gfx::RectF* opaque,
     ContentLayerClient::GraphicsContextStatus gc_status) {
   if (!bitmap_.width() || !bitmap_.height())
     return;
@@ skipping 11 matching lines @@
   paint.setXfermodeMode(SkXfermode::kSrc_Mode);
   canvas->drawBitmap(bitmap_, 0, 0, &paint);
 }
 
 bool PictureImageLayer::FillsBoundsCompletely() const {
   // PictureImageLayer will always paint to the entire layer bounds.
   return true;
 }
 
 }  // namespace cc