[WIP] cc: Use reverse spiral iterator in tiling 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 139 matching lines @@
 Tile* EvictionTilePriorityQueue::PairedPictureLayerQueue::Top(
     TreePriority tree_priority) {
   DCHECK(!IsEmpty());
 
   WhichTree next_tree = NextTileIteratorTree(tree_priority);
   PictureLayerImpl::LayerEvictionTileIterator* next_iterator =
       next_tree == ACTIVE_TREE ? &active_iterator : &pending_iterator;
   DCHECK(*next_iterator);
 
   Tile* tile = **next_iterator;
-  DCHECK(std::find(returned_shared_tiles.begin(),
-                   returned_shared_tiles.end(),
-                   tile) == returned_shared_tiles.end());
+  DCHECK(returned_tiles_for_debug.find(tile) == returned_tiles_for_debug.end());
   return tile;
 }
 
 void EvictionTilePriorityQueue::PairedPictureLayerQueue::Pop(
     TreePriority tree_priority) {
   DCHECK(!IsEmpty());
 
   WhichTree next_tree = NextTileIteratorTree(tree_priority);
   PictureLayerImpl::LayerEvictionTileIterator* next_iterator =
       next_tree == ACTIVE_TREE ? &active_iterator : &pending_iterator;
   DCHECK(*next_iterator);
-  returned_shared_tiles.push_back(**next_iterator);
+  DCHECK(returned_tiles_for_debug.insert(**next_iterator).second);
   ++(*next_iterator);
 
-  if (IsEmpty())
-    return;
-
-  next_tree = NextTileIteratorTree(tree_priority);
-  next_iterator =
-      next_tree == ACTIVE_TREE ? &active_iterator : &pending_iterator;
-  while (std::find(returned_shared_tiles.begin(),
-                   returned_shared_tiles.end(),
-                   **next_iterator) != returned_shared_tiles.end()) {
-    ++(*next_iterator);
-    if (IsEmpty())
-      break;
-    next_tree = NextTileIteratorTree(tree_priority);
-    next_iterator =
-        next_tree == ACTIVE_TREE ? &active_iterator : &pending_iterator;
-  }
+  // If no empty, use Top to do DCHECK the next iterator.
+  DCHECK(IsEmpty() || Top(tree_priority));
 }
 
 WhichTree
 EvictionTilePriorityQueue::PairedPictureLayerQueue::NextTileIteratorTree(
     TreePriority tree_priority) const {
   DCHECK(!IsEmpty());
 
   // If we only have one iterator with tiles, return it.
   if (!active_iterator)
     return PENDING_TREE;
   if (!pending_iterator)
     return ACTIVE_TREE;
 
   const Tile* active_tile = *active_iterator;
   const Tile* pending_tile = *pending_iterator;
   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 (active_priority.priority_bin == pending_priority.priority_bin) {
+    if (active_tile->required_for_activation()) {
+      if (!pending_tile->required_for_activation())
+        return PENDING_TREE;
+    } else if (pending_tile->required_for_activation()) {
+      return ACTIVE_TREE;
+    }
+  }
+
   if (pending_priority.IsHigherPriorityThan(active_priority))
     return ACTIVE_TREE;
   return PENDING_TREE;
 }
 
 }  // namespace cc