Add a compositing display item which replaces transparency display item

cc/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("//testing/test.gni")
 
 component("cc") {
   sources = [
     "animation/animation.cc",
     "animation/animation.h",
@@ skipping 326 matching lines @@
     "resources/bitmap_content_layer_updater.cc",
     "resources/bitmap_content_layer_updater.h",
     "resources/bitmap_skpicture_content_layer_updater.cc",
     "resources/bitmap_skpicture_content_layer_updater.h",
     "resources/bitmap_tile_task_worker_pool.cc",
     "resources/bitmap_tile_task_worker_pool.h",
     "resources/clip_display_item.cc",
     "resources/clip_display_item.h",
     "resources/clip_path_display_item.cc",
     "resources/clip_path_display_item.h",
+    "resources/compositing_display_item.cc",
+    "resources/compositing_display_item.h",
     "resources/content_layer_updater.cc",
     "resources/content_layer_updater.h",
     "resources/display_item.cc",
     "resources/display_item.h",
     "resources/display_item_list.cc",
     "resources/display_item_list.h",
     "resources/display_list_raster_source.cc",
     "resources/display_list_raster_source.h",
     "resources/display_list_recording_source.cc",
     "resources/display_list_recording_source.h",
@@ skipping 561 matching lines @@
     "//media",
     "//skia",
     "//testing/gmock",
     "//testing/gtest",
     "//testing/perf",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 }