Use Mojo pipes to signal sync IPC events

gpu/ipc/service/BUILD.gn

 # Copyright 2016 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")
 import("//build/config/ui.gni")
 if (is_mac) {
   import("//build/config/mac/mac_sdk.gni")
 }
 
@@ skipping 126 matching lines @@
     ":test_support",
     "//base",
     "//base/test:run_all_unittests",
     "//base/test:test_support",
     "//gpu/command_buffer/common",
     "//gpu/command_buffer/common:gles2_utils",
     "//gpu/command_buffer/service",
     "//gpu/config",
     "//gpu/ipc/common",
     "//ipc:test_support",
+    "//mojo/edk/system",
     "//skia",
     "//testing/gmock",
     "//testing/gtest",
     "//third_party/mesa:mesa_headers",
     "//ui/gfx:test_support",
     "//ui/gl:gl_unittest_utils",
     "//ui/gl:test_support",
     "//url",
   ]
   libs = []
   if (is_android) {
     sources += [ "gpu_memory_buffer_factory_surface_texture_unittest.cc" ]
     deps += [ "//ui/android:ui_java" ]
   }
   if (is_mac) {
     sources += [ "gpu_memory_buffer_factory_io_surface_unittest.cc" ]
   }
   if (use_ozone) {
     sources += [ "gpu_memory_buffer_factory_ozone_native_pixmap_unittest.cc" ]
     deps += [ "//ui/ozone" ]
   }
 }