cc: Use multiple PrepareTiles approaches

cc/tiles/picture_layer_tiling.cc

 // 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.
 
 #include "cc/tiles/picture_layer_tiling.h"
 
 #include <algorithm>
 #include <cmath>
 #include <limits>
 #include <set>
@@ skipping 795 matching lines @@
 
   bool tile_is_visible = current_visible_rect_.Intersects(tile->content_rect());
   if (!tile_is_visible)
     return false;
 
   if (IsTileOccludedOnCurrentTree(tile))
     return false;
   return true;
 }
 
+bool PictureLayerTiling::RasterSourceCoversCurrentVisibleTiles() const {
+  gfx::Rect visible_rect_expanded_to_tile_bounds =
+      tiling_data_.ExpandRectToTileBounds(current_visible_rect_);
+
+  return raster_source_->CoversRect(visible_rect_expanded_to_tile_bounds,
+                                    contents_scale_);
+}
+
 void PictureLayerTiling::UpdateRequiredStatesOnTile(Tile* tile) const {
   DCHECK(tile);
   tile->set_required_for_activation(IsTileRequiredForActivation(tile));
   tile->set_required_for_draw(IsTileRequiredForDraw(tile));
 }
 
 PrioritizedTile PictureLayerTiling::MakePrioritizedTile(
     Tile* tile,
     PriorityRectType priority_rect_type) const {
   DCHECK(tile);
@@ skipping 254 matching lines @@
       break;
   }
 
   gfx::Rect result(origin_x, origin_y, width, height);
   if (cache)
     cache->previous_result = result;
   return result;
 }
 
 }  // namespace cc