cc: Early out of UpdateTiles for resoureceless draw

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 818 matching lines @@
     LayerTreeImpl* sync_tree = layer_tree_host_impl_->CommitToActiveTree()
                                    ? layer_tree_host_impl_->active_tree()
                                    : layer_tree_host_impl_->pending_tree();
     // If this is not the sync tree, then it is not safe to update lcd text
     // as it causes invalidations and the tiles may be in use.
     DCHECK_EQ(this, sync_tree);
     for (const auto& layer : picture_layers_)
       layer->UpdateCanUseLCDTextAfterCommit();
   }
 
-  {
+  // Resourceless draw do not need tiles and should not affect existing tile
+  // priorities.
+  if (layer_tree_host_impl_->GetDrawMode() != DRAW_MODE_RESOURCELESS_SOFTWARE) {
     TRACE_EVENT_BEGIN2("cc", "LayerTreeImpl::UpdateDrawProperties::UpdateTiles",
                        "IsActive", IsActiveTree(), "SourceFrameNumber",
                        source_frame_number_);
-    const bool resourceless_software_draw =
-        (layer_tree_host_impl_->GetDrawMode() ==
-         DRAW_MODE_RESOURCELESS_SOFTWARE);
     size_t layers_updated_count = 0;
     bool tile_priorities_updated = false;
     for (PictureLayerImpl* layer : picture_layers_) {
       if (!layer->IsDrawnRenderSurfaceLayerListMember())
         continue;
       ++layers_updated_count;
-      tile_priorities_updated |= layer->UpdateTiles(resourceless_software_draw);
+      tile_priorities_updated |= layer->UpdateTiles();
     }
 
     if (tile_priorities_updated)
       DidModifyTilePriorities();
 
     TRACE_EVENT_END1("cc", "LayerTreeImpl::UpdateDrawProperties::UpdateTiles",
                      "layers_updated_count", layers_updated_count);
   }
 
   DCHECK(!needs_update_draw_properties_) <<
@@ skipping 1212 matching lines @@
                                                    const gfx::BoxF& box,
                                                    gfx::BoxF* bounds) const {
   *bounds = gfx::BoxF();
   return layer_tree_host_impl_->animation_host()
              ? layer_tree_host_impl_->animation_host()
                    ->TransformAnimationBoundsForBox(layer->id(), box, bounds)
              : true;
 }
 
 }  // namespace cc