mojo/public: Include gtest.h as "gtest/gtest.h", instead of via "absolute" path.

mojo/public/cpp/bindings/tests/callback_unittest.cc

 // Copyright 2015 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.
 
+#include "gtest/gtest.h"
 #include "mojo/public/cpp/bindings/callback.h"
 #include "mojo/public/cpp/bindings/map.h"
 #include "mojo/public/cpp/bindings/string.h"
-#include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
 namespace test {
 namespace {
 
 struct RunnableNoArgs {
   explicit RunnableNoArgs(int* calls) : calls(calls) {}
 
   void Run() const { (*calls)++; }
   int* calls;
@@ skipping 137 matching lines @@
   g_overloaded_function_with_double_param_called = false;
   mojo::Callback<void(double)> cb_with_double_param = &OverloadedFunction;
   cb_with_double_param.Run(123);
   EXPECT_TRUE(g_overloaded_function_with_double_param_called);
   g_overloaded_function_with_double_param_called = false;
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace mojo