cc: Add flag to disable future mask tiling.

cc/trees/layer_tree_settings.cc

Index: cc/trees/layer_tree_settings.cc
diff --git a/cc/trees/layer_tree_settings.cc b/cc/trees/layer_tree_settings.cc
index 6890bbb828e0bb7f5e44c60e0b654c9f001474cd..f4f404ac55be9ec009675f3f0cf6c229ca061154 100644
--- a/cc/trees/layer_tree_settings.cc
+++ b/cc/trees/layer_tree_settings.cc
@@ -77,6 +77,7 @@ bool LayerTreeSettings::operator==(const LayerTreeSettings& other) const {
              other.max_staging_buffer_usage_in_bytes &&
          gpu_memory_policy == other.gpu_memory_policy &&
          software_memory_policy == other.software_memory_policy &&
+         enable_mask_tiling == other.enable_mask_tiling &&
          LayerTreeDebugState::Equal(initial_debug_state,
                                     other.initial_debug_state);
 }