cc: Prevent the tile manager from allocating more memory than allowed.

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 7cf5096ce3b0db931de4b92c56b4b1bd4a54f9f0..8ece30bb0f0594a27a0b330af6ec29c61ba7a9cf 100644
--- a/cc/resources/tile_manager.cc
+++ b/cc/resources/tile_manager.cc
@@ -509,9 +509,10 @@ void TileManager::AssignGpuMemoryToTiles(
       static_cast<int64>(bytes_releasable) +
       static_cast<int64>(global_state_.memory_limit_in_bytes) -
       static_cast<int64>(resource_pool_->acquired_memory_usage_bytes());
-  int resources_available = resources_releasable +
-                            global_state_.num_resources_limit -
-                            resource_pool_->NumResources();
+  int resources_available =
+      resources_releasable +
+      global_state_.num_resources_limit -
+      resource_pool_->acquired_resource_count();
 
   size_t bytes_allocatable =
       std::max(static_cast<int64>(0), bytes_available);
@@ -709,6 +710,10 @@ void TileManager::ScheduleTasks(
     tasks.Append(tile_version.raster_task_, tile->required_for_activation());
   }
 
+  // We must reduce the amount of unused memory before calling
+  // ScheduleTasks to prevent usage from rising above limit.
+  resource_pool_->ReduceMemoryUsage();
+
   // Schedule running of |tasks|. This replaces any previously
   // scheduled tasks and effectively cancels all tasks not present
   // in |tasks|.