cc: Start using raster/eviction iterators in tile manager

cc/resources/picture_layer_tiling.cc

Index: cc/resources/picture_layer_tiling.cc
diff --git a/cc/resources/picture_layer_tiling.cc b/cc/resources/picture_layer_tiling.cc
index d2a732d9eb985e12d15a71405dde751458eb14b2..fc33acf5eb7356e60aa0db5e46af3e95c2d3a718 100644
--- a/cc/resources/picture_layer_tiling.cc
+++ b/cc/resources/picture_layer_tiling.cc
@@ -772,6 +772,8 @@ void PictureLayerTiling::UpdateEvictionCacheIfNeeded(
   eviction_tiles_cache_.clear();
   eviction_tiles_cache_.reserve(tiles_.size());
   for (TileMap::iterator it = tiles_.begin(); it != tiles_.end(); ++it) {
+    DCHECK(it->second);
+
     // TODO(vmpstr): This should update the priority if UpdateTilePriorities
     // changes not to do this.
     eviction_tiles_cache_.push_back(it->second);
@@ -818,6 +820,21 @@ PictureLayerTiling::TilingRasterTileIterator::TilingRasterTileIterator(
 
 PictureLayerTiling::TilingRasterTileIterator::~TilingRasterTileIterator() {}
 
+bool
+PictureLayerTiling::TilingRasterTileIterator::HasTilesRequiredForActivation()
+    const {
+  if (!*this || get_type() != TilePriority::NOW)
+    return false;
+
+  for (TilingData::Iterator it = visible_iterator_; it; ++it) {
+    std::pair<int, int> next_index = visible_iterator_.index();
+    Tile* tile = tiling_->TileAt(next_index.first, next_index.second);
+    if (tile && tile->required_for_activation())
+      return true;
+  }
+  return false;
+}
+
 void PictureLayerTiling::TilingRasterTileIterator::AdvancePhase() {
   DCHECK_LT(type_, TilePriority::EVENTUALLY);