cc: Use reverse spiral iterator in tiling eviction.

cc/layers/picture_layer_impl.cc

Index: cc/layers/picture_layer_impl.cc
diff --git a/cc/layers/picture_layer_impl.cc b/cc/layers/picture_layer_impl.cc
index 14dfa52efbcbad384591d6c3f7473f46b91af9b1..fbc57d9fa93201332724a47e828a97557d84c03b 100644
--- a/cc/layers/picture_layer_impl.cc
+++ b/cc/layers/picture_layer_impl.cc
@@ -1560,17 +1560,14 @@ void PictureLayerImpl::LayerRasterTileIterator::AdvanceToNextStage() {
 
 PictureLayerImpl::LayerEvictionTileIterator::LayerEvictionTileIterator()
     : layer_(nullptr),
-      tree_priority_(SAME_PRIORITY_FOR_BOTH_TREES),
       current_category_(PictureLayerTiling::EVENTUALLY),
       current_tiling_range_type_(PictureLayerTilingSet::HIGHER_THAN_HIGH_RES),
       current_tiling_(0u) {
 }
 
 PictureLayerImpl::LayerEvictionTileIterator::LayerEvictionTileIterator(
-    PictureLayerImpl* layer,
-    TreePriority tree_priority)
+    PictureLayerImpl* layer)
     : layer_(layer),
-      tree_priority_(tree_priority),
       current_category_(PictureLayerTiling::EVENTUALLY),
       current_tiling_range_type_(PictureLayerTilingSet::HIGHER_THAN_HIGH_RES),
       current_tiling_(CurrentTilingRange().start - 1u) {
@@ -1584,7 +1581,6 @@ PictureLayerImpl::LayerEvictionTileIterator::LayerEvictionTileIterator(
 
     current_iterator_ = PictureLayerTiling::TilingEvictionTileIterator(
         layer_->tilings_->tiling_at(CurrentTilingIndex()),
-        tree_priority,
         current_category_);
   } while (!current_iterator_);
 }
@@ -1613,7 +1609,6 @@ operator++() {
 
     current_iterator_ = PictureLayerTiling::TilingEvictionTileIterator(
         layer_->tilings_->tiling_at(CurrentTilingIndex()),
-        tree_priority_,
         current_category_);
   }
   return *this;
@@ -1626,16 +1621,9 @@ PictureLayerImpl::LayerEvictionTileIterator::operator bool() const {
 bool PictureLayerImpl::LayerEvictionTileIterator::AdvanceToNextCategory() {
   switch (current_category_) {
     case PictureLayerTiling::EVENTUALLY:
-      current_category_ =
-          PictureLayerTiling::EVENTUALLY_AND_REQUIRED_FOR_ACTIVATION;
-      return true;
-    case PictureLayerTiling::EVENTUALLY_AND_REQUIRED_FOR_ACTIVATION:
       current_category_ = PictureLayerTiling::SOON;
       return true;
     case PictureLayerTiling::SOON:
-      current_category_ = PictureLayerTiling::SOON_AND_REQUIRED_FOR_ACTIVATION;
-      return true;
-    case PictureLayerTiling::SOON_AND_REQUIRED_FOR_ACTIVATION:
       current_category_ = PictureLayerTiling::NOW;
       return true;
     case PictureLayerTiling::NOW: