cc: Optimize decode scheduling for checker-images.

cc/tiles/picture_layer_tiling.cc

Index: cc/tiles/picture_layer_tiling.cc
diff --git a/cc/tiles/picture_layer_tiling.cc b/cc/tiles/picture_layer_tiling.cc
index b429260472a1a0d523c50d1565cbc9309a2cabe3..21b1633b46c411c2a8d9fc9d44167d21dc1d20a0 100644
--- a/cc/tiles/picture_layer_tiling.cc
+++ b/cc/tiles/picture_layer_tiling.cc
@@ -815,6 +815,35 @@ bool PictureLayerTiling::IsTileRequiredForDraw(const Tile* tile) const {
   return true;
 }
 
+bool PictureLayerTiling::ShouldProcessTileForCheckerImages(

[Khushal, 2017/04/11 22:45:22]

This one was to skip tiles on the active tree if they are going to be
replaced/occluded upon activation. Since anything we invalidate should be on
this pending tree (after it gets activated).

+    const Tile* tile) const {
+  // If this is the pending tree and the tile is not occluded, it needs to be
+  // processed for checker-images.
+  if (tree_ == PENDING_TREE)
+    return !IsTileOccludedOnCurrentTree(tile);
+
+  DCHECK_EQ(tree_, ACTIVE_TREE);
+  const PictureLayerTiling* pending_twin =
+      client_->GetPendingOrActiveTwinTiling(this);
+
+  // If we don't have a pending twin, the tiling may be evicted upon activation,
+  // or we may not have a pending tree. So use the occlusion on the current
+  // tree.
+  if (!pending_twin)
+    return !IsTileOccludedOnCurrentTree(tile);
+
+  // If the tile will be replaced upon activation, then we don't need to process
+  // it for checkered images. Since it is the active tree's content that we will
+  // invalidate and replace once the decode finishes.
+  if (!TilingMatchesTileIndices(pending_twin) ||
+      pending_twin->TileAt(tile->tiling_i_index(), tile->tiling_j_index())) {
+    return false;
+  }
+
+  // Ask the pending twin if this tile will become occluded upon activation.
+  return !pending_twin->IsTileOccludedOnCurrentTree(tile);
+}
+
 void PictureLayerTiling::UpdateRequiredStatesOnTile(Tile* tile) const {
   tile->set_required_for_activation(IsTileRequiredForActivation(tile));
   tile->set_required_for_draw(IsTileRequiredForDraw(tile));
@@ -842,7 +871,8 @@ PrioritizedTile PictureLayerTiling::MakePrioritizedTile(
        tile_priority.distance_to_visible >
            0.5f * max_skewport_extent_in_screen_space_);
   return PrioritizedTile(tile, this, tile_priority, IsTileOccluded(tile),
-                         process_for_images_only);
+                         process_for_images_only,
+                         ShouldProcessTileForCheckerImages(tile));
 }
 
 std::map<const Tile*, PrioritizedTile>