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

cc/layers/picture_layer_impl.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/layers/picture_layer_impl.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 497 matching lines @@
   // - This layer produced a high-res or non-ideal-res tile last frame.
   // - We're in requires high res to draw mode.
   // - We're not in smoothness takes priority mode.
   // To put different, the tiling set can't require tiles for activation if
   // we're in smoothness mode and only used low-res or checkerboard to draw last
   // frame and we don't need high res to draw.
   //
   // The reason for this is that we should be able to activate sooner and get a
   // more up to date recording, so we don't run out of recording on the active
   // tree.
-  bool can_require_tiles_for_activation =
+  // A layer must be a drawing layer for it to require tiles for activation.
+  bool can_require_tiles_for_activation = contributes_to_drawn_render_surface();

[Khushal, 2017/05/24 21:57:06]

Should this be done for requiring tiles for draw as well? I'm guessing there
wouldn't be much impact in the renderer from that right now since we don't block
drawing on ReadyToDraw there.

+  can_require_tiles_for_activation &=
       !only_used_low_res_last_append_quads_ || RequiresHighResToDraw() ||
       !layer_tree_impl()->SmoothnessTakesPriority();
 
   static const Occlusion kEmptyOcclusion;
   const Occlusion& occlusion_in_content_space =
       layer_tree_impl()->settings().use_occlusion_for_tile_prioritization
           ? draw_properties().occlusion_in_content_space
           : kEmptyOcclusion;
 
   // Pass |occlusion_in_content_space| for |occlusion_in_layer_space| since
@@ skipping 950 matching lines @@
   }
 
   invalidation_.Union(invalidation);
   tilings_->UpdateTilingsForImplSideInvalidation(invalidation);
   SetNeedsPushProperties();
   TRACE_EVENT_END1("cc", "PictureLayerImpl::InvalidateRegionForImages",
                    "Invalidation", invalidation.ToString());
 }
 
 }  // namespace cc