Revert of Mojo multiple command buffer support and sample

mojo/services/native_viewport/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/ui.gni")
 import("//mojo/system.gni")
 
 static_library("native_viewport") {
   output_name = "mojo_native_viewport"
 
   deps = [
     "//base",
     "//ui/events",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//mojo/public/cpp/application:chromium",
     "//mojo/common",
     "//mojo/environment:chromium",
     "//mojo/services/public/cpp/geometry",
     "//mojo/services/public/interfaces/geometry",
     "//mojo/services/gles2",
     "//mojo/services/public/cpp/input_events",
     "//mojo/services/public/interfaces/native_viewport",
   ]
 
   sources = [
-    "gpu_impl.cc",
-    "gpu_impl.h",
     "native_viewport_impl.cc",
     "native_viewport_impl.h",
     "platform_viewport.h",
     "platform_viewport_android.cc",
     "platform_viewport_android.h",
     "platform_viewport_mac.mm",
     "platform_viewport_win.cc",
   ]
 
   if (is_ios) {
@@ skipping 13 matching lines @@
 
   if (use_x11) {
     sources += [ "platform_viewport_x11.cc" ]
     deps += [ "//ui/platform_window/x11" ]
   }
 
   if (use_ozone) {
     sources += [ "platform_viewport_ozone.cc" ]
   }
 }