cc: Add command line switch to control resource usage for impl-side painting.

cc/resources/tile_manager.cc

Index: cc/resources/tile_manager.cc
diff --git a/cc/resources/tile_manager.cc b/cc/resources/tile_manager.cc
index 10f9179032c1ddc420a91516ed4c4dbec8690889..386aaf8dc96cc30cde313e7f7fa976bf2e8a425f 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -922,8 +922,14 @@ void TileManager::OnRasterTaskCompleted(
 void TileManager::DidFinishTileInitialization(Tile* tile) {
   ManagedTileState& managed_state = tile->managed_state();
   managed_state.drawing_info.resource_is_being_initialized_ = false;
+
   if (tile->priority(ACTIVE_TREE).distance_to_visible_in_pixels == 0)
     client_->DidInitializeVisibleTile();
+
+  // Reduce memory usage when no work is pending.
+  if (!HasPendingWorkScheduled(PENDING_TREE) &&
+      !HasPendingWorkScheduled(ACTIVE_TREE))
+    resource_pool_->ReduceMemoryUsage();
 }
 
 void TileManager::DidTileRasterStateChange(Tile* tile, TileRasterState state) {