cc: Implement geometry-based tile eviction

cc/resources/eviction_tile_priority_queue.cc

 // Copyright 2014 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/resources/eviction_tile_priority_queue.h"
 
 namespace cc {
 
 namespace {
 
@@ skipping 182 matching lines @@
   DCHECK(!IsEmpty());
 
   // If we only have one iterator with tiles, return it.
   if (!active_queue || active_queue->IsEmpty())
     return PENDING_TREE;
   if (!pending_queue || pending_queue->IsEmpty())
     return ACTIVE_TREE;
 
   const Tile* active_tile = active_queue->Top();
   const Tile* pending_tile = pending_queue->Top();
+
+  // If tiles are the same, it doesn't matter which tree we return.
   if (active_tile == pending_tile)
     return ACTIVE_TREE;
 
   const TilePriority& active_priority =
       active_tile->priority_for_tree_priority(tree_priority);
   const TilePriority& pending_priority =
       pending_tile->priority_for_tree_priority(tree_priority);
 
+  // If the bins are the same and activation differs, then return the tree of
+  // the tile not required for activation.
+  if (active_priority.priority_bin == pending_priority.priority_bin &&
+      active_tile->required_for_activation() !=
+          pending_tile->required_for_activation()) {
+    return active_tile->required_for_activation() ? PENDING_TREE : ACTIVE_TREE;
+  }
+
+  // Return tile with a lower priority.
   if (pending_priority.IsHigherPriorityThan(active_priority))
     return ACTIVE_TREE;
   return PENDING_TREE;
 }
 
 }  // namespace cc