Add tracing service and make the shell+sky_viewer+services talk to it

mojo/services/window_manager/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/public/mojo_application.gni")
 
 mojo_native_application("window_manager") {
   sources = [ "main.cc" ]
 
   public_deps = [
     ":lib",
   ]
 
   deps = [
     "//base",
     "//mojo/application",
+    "//mojo/common:tracing_impl",
     "//mojo/public/c/system:for_shared_library",
     "//mojo/services/public/cpp/view_manager",
   ]
 }
 
 source_set("lib") {
   sources = [
     "basic_focus_rules.cc",
     "basic_focus_rules.h",
     "focus_controller.cc",
@@ skipping 63 matching lines @@
     "//ui/events:test_support",
     "//ui/gfx",
     "//ui/gfx:test_support",
     "//ui/gl",
   ]
 
   if (use_x11) {
     deps += [ "//ui/gfx/x" ]
   }
 }