Add a copy of webrtc's TaskRunner abstraction, which is going to be deleted in webrtc.

remoting/client/display/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.
 
 source_set("display") {
   sources = [
     "canvas.h",
     "drawable.h",
     "gl_canvas.cc",
     "gl_canvas.h",
@@ skipping 13 matching lines @@
     "gl_render_layer.h",
     "gl_renderer.cc",
     "gl_renderer.h",
     "sys_opengl.h",
   ]
 
   deps = [
     "//remoting/proto",
     "//third_party/libyuv",
     "//third_party/webrtc/base:rtc_base",
-    "//third_party/webrtc/base:rtc_task_runner",
   ]
 
   public_configs = [ "//third_party/khronos:khronos_headers" ]
 
   if (is_android) {
     libs = [ "GLESv2" ]
   }
 
   if (is_linux) {
     libs = [ "GL" ]
@@ skipping 35 matching lines @@
       "//remoting/build/config:version",
       "//remoting/build/config:enable_webrtc_remoting_client",
     ]
 
     deps = [
       ":display",
       "//remoting/proto",
       "//testing/gmock",
       "//testing/gtest",
       "//third_party/webrtc/base:rtc_base",
-      "//third_party/webrtc/base:rtc_task_runner",
     ]
   }
 }