Revert of Remove enable/disable wheel gestures setting.

cc/trees/layer_tree_settings.h

Index: cc/trees/layer_tree_settings.h
diff --git a/cc/trees/layer_tree_settings.h b/cc/trees/layer_tree_settings.h
index 64a8258c0d9751ca5323acfb96c8db183c51bd91..d20da52efacd7ecb987bc562bd758e4d6a1d2ae4 100644
--- a/cc/trees/layer_tree_settings.h
+++ b/cc/trees/layer_tree_settings.h
@@ -94,6 +94,7 @@
   bool image_decode_tasks_enabled = false;
   bool wait_for_beginframe_interval = true;
   bool abort_commit_before_output_surface_creation = true;
+  bool use_mouse_wheel_gestures = false;
   bool use_layer_lists = false;
   int max_staging_buffer_usage_in_bytes = 32 * 1024 * 1024;
   ManagedMemoryPolicy memory_policy_;