Keeping track of descendants that draw content instead of recalcualting

cc/layers/tiled_layer.cc

 // Copyright 2011 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/tiled_layer.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/auto_reset.h"
@@ skipping 136 matching lines @@
   if (old_tiling_size == new_tiling_size)
     return;
   tiler_->SetTilingSize(new_tiling_size);
 
   // Invalidate any areas that the new bounds exposes.
   Region new_region =
       SubtractRegions(gfx::Rect(new_tiling_size), gfx::Rect(old_tiling_size));
   for (Region::Iterator new_rects(new_region); new_rects.has_rect();
        new_rects.next())
     InvalidateContentRect(new_rects.rect());
+  UpdateDrawsContent(HasDrawableContent());
 }
 
 void TiledLayer::SetTileSize(const gfx::Size& size) {
   tiler_->SetTileSize(size);
+  UpdateDrawsContent(HasDrawableContent());
 }
 
 void TiledLayer::SetBorderTexelOption(
     LayerTilingData::BorderTexelOption border_texel_option) {
   tiler_->SetBorderTexelOption(border_texel_option);
+  UpdateDrawsContent(HasDrawableContent());
 }
 
-bool TiledLayer::DrawsContent() const {
-  if (!ContentsScalingLayer::DrawsContent())
-    return false;
+bool TiledLayer::HasDrawableContent() const {
+  bool has_more_than_one_tile =
+      (tiler_->num_tiles_x() > 1) || (tiler_->num_tiles_y() > 1);
 
-  bool has_more_than_one_tile =
-      tiler_->num_tiles_x() > 1 || tiler_->num_tiles_y() > 1;
-  if (tiling_option_ == NEVER_TILE && has_more_than_one_tile)
-    return false;
-
-  return true;
+  return !(tiling_option_ == NEVER_TILE && has_more_than_one_tile) &&
+         ContentsScalingLayer::HasDrawableContent();
 }
 
 void TiledLayer::ReduceMemoryUsage() {
   if (Updater())
     Updater()->ReduceMemoryUsage();
 }
 
 void TiledLayer::SetIsMask(bool is_mask) {
   set_tiling_option(is_mask ? NEVER_TILE : AUTO_TILE);
 }
@@ skipping 704 matching lines @@
   gfx::Rect prepaint_rect = visible_content_rect();
   prepaint_rect.Inset(-tiler_->tile_size().width() * kPrepaintColumns,
                       -tiler_->tile_size().height() * kPrepaintRows);
   gfx::Rect content_rect(content_bounds());
   prepaint_rect.Intersect(content_rect);
 
   return prepaint_rect;
 }
 
 }  // namespace cc