cc: Use reverse spiral iterator in tiling eviction.

cc/resources/tile_manager_unittest.cc

 // Copyright 2013 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"
 #include "cc/resources/raster_tile_priority_queue.h"
 #include "cc/resources/tile.h"
 #include "cc/resources/tile_priority.h"
 #include "cc/test/fake_impl_proxy.h"
 #include "cc/test/fake_layer_tree_host_impl.h"
@@ skipping 384 matching lines @@
 
   tile_manager()->InitializeTilesWithResourcesForTesting(
       std::vector<Tile*>(all_tiles.begin(), all_tiles.end()));
 
   Tile* last_tile = NULL;
   smoothness_tiles.clear();
   tile_count = 0;
   // Here we expect to get increasing ACTIVE_TREE priority_bin.
   queue.Reset();
   host_impl_.BuildEvictionQueue(&queue, SMOOTHNESS_TAKES_PRIORITY);
+  int distance_increasing = 0;
+  int distance_decreasing = 0;
   while (!queue.IsEmpty()) {
     Tile* tile = queue.Top();
     EXPECT_TRUE(tile);
     EXPECT_TRUE(tile->HasResources());
 
     if (!last_tile)
       last_tile = tile;
 
     EXPECT_GE(last_tile->priority(ACTIVE_TREE).priority_bin,
               tile->priority(ACTIVE_TREE).priority_bin);
     if (last_tile->priority(ACTIVE_TREE).priority_bin ==
         tile->priority(ACTIVE_TREE).priority_bin) {
       EXPECT_LE(last_tile->required_for_activation(),
                 tile->required_for_activation());
       if (last_tile->required_for_activation() ==
           tile->required_for_activation()) {
-        EXPECT_GE(last_tile->priority(ACTIVE_TREE).distance_to_visible,
-                  tile->priority(ACTIVE_TREE).distance_to_visible);
+        if (last_tile->priority(ACTIVE_TREE).distance_to_visible >=
+            tile->priority(ACTIVE_TREE).distance_to_visible) {
+          ++distance_decreasing;
+        } else {
+          ++distance_increasing;
+        }
       }
     }
 
     last_tile = tile;
     ++tile_count;
     smoothness_tiles.insert(tile);
     queue.Pop();
   }
 
+  EXPECT_EQ(4, distance_increasing);
+  EXPECT_EQ(15, distance_decreasing);
   EXPECT_EQ(tile_count, smoothness_tiles.size());
   EXPECT_EQ(all_tiles, smoothness_tiles);
 
   std::set<Tile*> new_content_tiles;
   last_tile = NULL;
   // Here we expect to get increasing PENDING_TREE priority_bin.
   queue.Reset();
   host_impl_.BuildEvictionQueue(&queue, NEW_CONTENT_TAKES_PRIORITY);
+  distance_increasing = 0;
+  distance_decreasing = 0;
   while (!queue.IsEmpty()) {
     Tile* tile = queue.Top();
     EXPECT_TRUE(tile);
 
     if (!last_tile)
       last_tile = tile;
 
     EXPECT_GE(last_tile->priority(PENDING_TREE).priority_bin,
               tile->priority(PENDING_TREE).priority_bin);
     if (last_tile->priority(PENDING_TREE).priority_bin ==
         tile->priority(PENDING_TREE).priority_bin) {
       EXPECT_LE(last_tile->required_for_activation(),
                 tile->required_for_activation());
       if (last_tile->required_for_activation() ==
           tile->required_for_activation()) {
-        EXPECT_GE(last_tile->priority(PENDING_TREE).distance_to_visible,
-                  tile->priority(PENDING_TREE).distance_to_visible);
+        if (last_tile->priority(PENDING_TREE).distance_to_visible >=
+            tile->priority(PENDING_TREE).distance_to_visible) {
+          ++distance_decreasing;
+        } else {
+          ++distance_increasing;
+        }
       }
     }
 
     last_tile = tile;
     new_content_tiles.insert(tile);
     queue.Pop();
   }
 
+  EXPECT_EQ(4, distance_increasing);
+  EXPECT_EQ(15, distance_decreasing);
+
   EXPECT_EQ(tile_count, new_content_tiles.size());
   EXPECT_EQ(all_tiles, new_content_tiles);
 }
 
 TEST_F(TileManagerTilePriorityQueueTest,
        EvictionTilePriorityQueueWithOcclusion) {
   gfx::Size tile_size(102, 102);
   gfx::Size layer_bounds(1000, 1000);
 
   scoped_refptr<FakePicturePileImpl> pending_pile =
@@ skipping 196 matching lines @@
     all_tiles.insert(queue.Top());
     ++tile_count;
     queue.Pop();
   }
   EXPECT_EQ(tile_count, all_tiles.size());
   EXPECT_EQ(17u, tile_count);
 }
 
 }  // namespace
 }  // namespace cc