cc: Give non-drawing layers that are rasterized a lower priority.

cc/trees/layer_tree_impl.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/trees/layer_tree_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1126 matching lines @@
 
   // Resourceless draw do not need tiles and should not affect existing tile
   // priorities.
   if (!is_in_resourceless_software_draw_mode()) {
     TRACE_EVENT_BEGIN2("cc", "LayerTreeImpl::UpdateDrawProperties::UpdateTiles",
                        "IsActive", IsActiveTree(), "SourceFrameNumber",
                        source_frame_number_);
     size_t layers_updated_count = 0;
     bool tile_priorities_updated = false;
     for (PictureLayerImpl* layer : picture_layers_) {
-      if (!layer->contributes_to_drawn_render_surface())
+      if (!layer->HasValidTilePriorities())

[danakj, 2017/05/25 15:49:02]

Is there a test for this?

[Khushal, 2017/05/25 22:43:23]

Done. UpdatedTilingsForNonDrawingLayers.

         continue;
       ++layers_updated_count;
       tile_priorities_updated |= layer->UpdateTiles();
     }
 
     if (tile_priorities_updated)
       DidModifyTilePriorities();
 
     TRACE_EVENT_END1("cc", "LayerTreeImpl::UpdateDrawProperties::UpdateTiles",
                      "layers_updated_count", layers_updated_count);
@@ skipping 959 matching lines @@
 
 void LayerTreeImpl::ResetAllChangeTracking() {
   layers_that_should_push_properties_.clear();
   // Iterate over all layers, including masks.
   for (auto& layer : *layers_)
     layer->ResetChangeTracking();
   property_trees_.ResetAllChangeTracking();
 }
 
 }  // namespace cc