cc: Optimize decode scheduling for checker-images.

cc/tiles/picture_layer_tiling.h

 // Copyright 2012 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.
 
 #ifndef CC_TILES_PICTURE_LAYER_TILING_H_
 #define CC_TILES_PICTURE_LAYER_TILING_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 87 matching lines @@
 
   void SetRasterSourceAndResize(scoped_refptr<RasterSource> raster_source);
   void Invalidate(const Region& layer_invalidation);
   void CreateMissingTilesInLiveTilesRect();
   void TakeTilesAndPropertiesFrom(PictureLayerTiling* pending_twin,
                                   const Region& layer_invalidation);
 
   bool IsTileRequiredForActivation(const Tile* tile) const;
   bool IsTileRequiredForDraw(const Tile* tile) const;
 
+  // Returns true if the tile should be processed for decoding images skipped

[vmpstr, 2017/04/18 00:20:00]

Can you rephrase this a bit (it sounds confusing to me).

Maybe something like

// During raster, some tiles maybe have been rasterized with images skipped. We
still need to process these tiles to ensure we can retrieve the images that need
to be decoded. This function returns true if the given tile is one of these
skipped images tiles that need to processed. 

[Khushal, 2017/04/19 06:16:41]

Its actually not necessary that images were skipped for this tile. Its possible
for a tile on the active tree to become visible while there is a pending tree
tile that will replace it. In which case, we still skip the image for the active
tree tile, but we don't decode it because it won't be present after activation.

That's why I went with ShouldDecodeCheckeredImageForTile, whether we need to
decode the images already skipped, or to be skipped, for this tile.

+  // during rasterization.
+  bool ShouldDecodeCheckeredImagesForTile(const Tile* tile) const;
+
   void set_resolution(TileResolution resolution) {
     resolution_ = resolution;
     may_contain_low_resolution_tiles_ |= resolution == LOW_RESOLUTION;
   }
   TileResolution resolution() const { return resolution_; }
   bool may_contain_low_resolution_tiles() const {
     return may_contain_low_resolution_tiles_;
   }
   void reset_may_contain_low_resolution_tiles() {
     may_contain_low_resolution_tiles_ = false;
@@ skipping 263 matching lines @@
   bool has_eventually_rect_tiles_ = false;
   bool all_tiles_done_ = true;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PictureLayerTiling);
 };
 
 }  // namespace cc
 
 #endif  // CC_TILES_PICTURE_LAYER_TILING_H_