[WIP] cc: Use reverse spiral iterator in tiling eviction.

cc/layers/picture_layer_impl_unittest.cc

Index: cc/layers/picture_layer_impl_unittest.cc
diff --git a/cc/layers/picture_layer_impl_unittest.cc b/cc/layers/picture_layer_impl_unittest.cc
index bd0585e52bab399da9b8245dd2d398d2a668225c..c78602ba8c5563ff7e5e6d45140611f5b5d2a0b9 100644
--- a/cc/layers/picture_layer_impl_unittest.cc
+++ b/cc/layers/picture_layer_impl_unittest.cc
@@ -2960,6 +2960,8 @@ TEST_F(PictureLayerImplTest, LayerEvictionTileIterator) {
   size_t scale_index = 0;
   bool reached_visible = false;
   Tile* last_tile = nullptr;
+  int distance_decreasing = 0;
+  int distance_increasing = 0;
   for (it = PictureLayerImpl::LayerEvictionTileIterator(
            pending_layer_, SAME_PRIORITY_FOR_BOTH_TREES);
        it;
@@ -2989,21 +2991,26 @@ TEST_F(PictureLayerImplTest, LayerEvictionTileIterator) {
     EXPECT_FLOAT_EQ(tile->contents_scale(), expected_scales[scale_index]);
     unique_tiles.insert(tile);
 
-    // If the tile is the same rough bin as last tile (same activation, bin, and
-    // scale), then distance should be decreasing.
     if (tile->required_for_activation() ==
             last_tile->required_for_activation() &&
         priority.priority_bin ==
             last_tile->priority(PENDING_TREE).priority_bin &&
         std::abs(tile->contents_scale() - last_tile->contents_scale()) <
             std::numeric_limits<float>::epsilon()) {
-      EXPECT_LE(priority.distance_to_visible,
-                last_tile->priority(PENDING_TREE).distance_to_visible);
+      if (priority.distance_to_visible <=
+          last_tile->priority(PENDING_TREE).distance_to_visible) {
+        ++distance_decreasing;
+      } else {
+        ++distance_increasing;
+      }
     }
 
     last_tile = tile;
   }
 
+  EXPECT_EQ(7, distance_increasing);
+  EXPECT_EQ(55, distance_decreasing);
+
   EXPECT_TRUE(reached_visible);
   EXPECT_EQ(65u, unique_tiles.size());
 
@@ -3812,40 +3819,41 @@ class OcclusionTrackingPictureLayerImplTest : public PictureLayerImplTest {
   OcclusionTrackingPictureLayerImplTest()
       : PictureLayerImplTest(OcclusionTrackingSettings()) {}
 
-  void VerifyEvictionConsidersOcclusion(
-      PictureLayerImpl* layer,
-      size_t expected_occluded_tile_count[NUM_TREE_PRIORITIES]) {
+  void VerifyEvictionConsidersOcclusion(FakePictureLayerImpl* layer,
+                                        FakePictureLayerImpl* twin_layer,
+                                        WhichTree tree,
+                                        size_t expected_occluded_tile_count) {
+    twin_layer->set_has_valid_tile_priorities(false);
     for (int priority_count = 0; priority_count < NUM_TREE_PRIORITIES;
          ++priority_count) {
       TreePriority tree_priority = static_cast<TreePriority>(priority_count);
       size_t occluded_tile_count = 0u;
       Tile* last_tile = nullptr;
+      std::set<Tile*> shared_tiles;
 
       for (PictureLayerImpl::LayerEvictionTileIterator it =
                PictureLayerImpl::LayerEvictionTileIterator(layer,
                                                            tree_priority);
-           it;
-           ++it) {
+           it; ++it) {
         Tile* tile = *it;
         if (!last_tile)
           last_tile = tile;
+        if (tile->is_shared())
+          EXPECT_TRUE(shared_tiles.insert(tile).second);
 
         // The only way we will encounter an occluded tile after an unoccluded
         // tile is if the priorty bin decreased, the tile is required for
         // activation, or the scale changed.
-        bool tile_is_occluded =
-            tile->is_occluded_for_tree_priority(tree_priority);
+        bool tile_is_occluded = tile->is_occluded(tree);
         if (tile_is_occluded) {
           occluded_tile_count++;
 
-          bool last_tile_is_occluded =
-              last_tile->is_occluded_for_tree_priority(tree_priority);
+          bool last_tile_is_occluded = last_tile->is_occluded(tree);
           if (!last_tile_is_occluded) {
             TilePriority::PriorityBin tile_priority_bin =
-                tile->priority_for_tree_priority(tree_priority).priority_bin;
+                tile->priority(tree).priority_bin;
             TilePriority::PriorityBin last_tile_priority_bin =
-                last_tile->priority_for_tree_priority(tree_priority)
-                    .priority_bin;
+                last_tile->priority(tree).priority_bin;
 
             EXPECT_TRUE(
                 (tile_priority_bin < last_tile_priority_bin) ||
@@ -3855,9 +3863,21 @@ class OcclusionTrackingPictureLayerImplTest : public PictureLayerImplTest {
         }
         last_tile = tile;
       }
-      EXPECT_EQ(expected_occluded_tile_count[priority_count],
-                occluded_tile_count);
+      for (PictureLayerImpl::LayerEvictionTileIterator it =
+               PictureLayerImpl::LayerEvictionTileIterator(twin_layer,
+                                                           tree_priority);
+           it; ++it) {
+        Tile* tile = *it;
+        if (tile->is_shared())
+          EXPECT_TRUE(shared_tiles.insert(tile).second);
+        else
+          continue;
+        if (tile->is_occluded(tree))
+          ++occluded_tile_count;
+      }
+      EXPECT_EQ(expected_occluded_tile_count, occluded_tile_count);
     }
+    twin_layer->set_has_valid_tile_priorities(true);
   }
 };
 
@@ -4330,11 +4350,7 @@ TEST_F(OcclusionTrackingPictureLayerImplTest,
   size_t expected_occluded_tile_count_on_active[] = {30u, 5u, 4u, 2u, 2u};
   size_t expected_occluded_tile_count_on_pending[] = {30u, 5u, 4u, 2u, 2u};
 
-  // The total expected number of occluded tiles on all tilings for each of the
-  // 3 tree priorities.
-  size_t total_expected_occluded_tile_count[] = {13u, 43u, 43u};
-
-  ASSERT_EQ(arraysize(total_expected_occluded_tile_count), NUM_TREE_PRIORITIES);
+  size_t total_expected_occluded_count_on_trees[] = {43u, 43u};
 
   // Verify number of occluded tiles on the pending layer for each tiling.
   for (size_t i = 0; i < pending_layer_->num_tilings(); ++i) {
@@ -4417,10 +4433,12 @@ TEST_F(OcclusionTrackingPictureLayerImplTest,
 
   host_impl_.tile_manager()->InitializeTilesWithResourcesForTesting(all_tiles);
 
-  VerifyEvictionConsidersOcclusion(pending_layer_,
-                                   total_expected_occluded_tile_count);
-  VerifyEvictionConsidersOcclusion(active_layer_,
-                                   total_expected_occluded_tile_count);
+  VerifyEvictionConsidersOcclusion(
+      pending_layer_, active_layer_, PENDING_TREE,
+      total_expected_occluded_count_on_trees[PENDING_TREE]);
+  VerifyEvictionConsidersOcclusion(
+      active_layer_, pending_layer_, ACTIVE_TREE,
+      total_expected_occluded_count_on_trees[ACTIVE_TREE]);
 }
 
 TEST_F(PictureLayerImplTest, PendingOrActiveTwinLayer) {