Add ink drop masking to TrayBackgroundView

ui/views/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/ozone/ozone.gni")
 
 config("flags") {
@@ skipping 17 matching lines @@
     "animation/ink_drop_animation_ended_reason.cc",
     "animation/ink_drop_animation_ended_reason.h",
     "animation/ink_drop_highlight.cc",
     "animation/ink_drop_highlight.h",
     "animation/ink_drop_highlight_observer.h",
     "animation/ink_drop_host.h",
     "animation/ink_drop_host_view.cc",
     "animation/ink_drop_host_view.h",
     "animation/ink_drop_impl.cc",
     "animation/ink_drop_impl.h",
+    "animation/ink_drop_mask.cc",
+    "animation/ink_drop_mask.h",
     "animation/ink_drop_painted_layer_delegates.cc",
     "animation/ink_drop_painted_layer_delegates.h",
     "animation/ink_drop_ripple.cc",
     "animation/ink_drop_ripple.h",
     "animation/ink_drop_ripple_observer.h",
     "animation/ink_drop_state.cc",
     "animation/ink_drop_state.h",
     "animation/ink_drop_stub.cc",
     "animation/ink_drop_stub.h",
     "animation/scroll_animator.cc",
@@ skipping 970 matching lines @@
       "//ui/base:test_support",
       "//ui/compositor",
       "//ui/events:test_support",
       "//ui/gl:test_support",
       "//ui/resources",
       "//ui/resources:ui_test_pak",
       "//ui/strings",
     ]
   }
 }