cc: Use reverse spiral iterator in tiling eviction.

cc/resources/picture_layer_tiling_perftest.cc

Index: cc/resources/picture_layer_tiling_perftest.cc
diff --git a/cc/resources/picture_layer_tiling_perftest.cc b/cc/resources/picture_layer_tiling_perftest.cc
index 0d1443eb50c9a569b4c418b4f80874e80c98b38c..f6cbbb09607b0724cbd934e2ae1c92ac723d2be4 100644
--- a/cc/resources/picture_layer_tiling_perftest.cc
+++ b/cc/resources/picture_layer_tiling_perftest.cc
@@ -189,16 +189,10 @@ class PictureLayerTilingPerfTest : public testing::Test {
         ACTIVE_TREE, viewport, 1.0f, 1.0, Occlusion());
 
     timer_.Reset();
-    TreePriority priorities[] = {SAME_PRIORITY_FOR_BOTH_TREES,
-                                 SMOOTHNESS_TAKES_PRIORITY,
-                                 NEW_CONTENT_TAKES_PRIORITY};
-    int priority_count = 0;
     do {
       PictureLayerTiling::TilingEvictionTileIterator it(
           picture_layer_tiling_.get(),
-          priorities[priority_count],
           PictureLayerTiling::NOW);
-      priority_count = (priority_count + 1) % arraysize(priorities);
       timer_.NextLap();
     } while (!timer_.HasTimeLimitExpired());
 
@@ -220,10 +214,6 @@ class PictureLayerTilingPerfTest : public testing::Test {
     picture_layer_tiling_->ComputeTilePriorityRects(
         ACTIVE_TREE, viewport, 1.0f, 1.0, Occlusion());
 
-    TreePriority priorities[] = {SAME_PRIORITY_FOR_BOTH_TREES,
-                                 SMOOTHNESS_TAKES_PRIORITY,
-                                 NEW_CONTENT_TAKES_PRIORITY};
-
     // Ensure all tiles have resources.
     std::vector<Tile*> all_tiles = picture_layer_tiling_->AllTilesForTesting();
     for (std::vector<Tile*>::iterator tile_it = all_tiles.begin();
@@ -235,20 +225,17 @@ class PictureLayerTilingPerfTest : public testing::Test {
           ScopedResource::Create(resource_provider_.get()).Pass());
     }
 
-    int priority_count = 0;
     timer_.Reset();
     do {
       int count = num_tiles;
       PictureLayerTiling::TilingEvictionTileIterator it(
           picture_layer_tiling_.get(),
-          priorities[priority_count],
           PictureLayerTiling::EVENTUALLY);
       while (count--) {
         ASSERT_TRUE(it) << "count: " << count;
         ASSERT_TRUE(*it != NULL) << "count: " << count;
         ++it;
       }
-      priority_count = (priority_count + 1) % arraysize(priorities);
       timer_.NextLap();
     } while (!timer_.HasTimeLimitExpired());