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

mojo/public/c/tests/bindings/buffer_unittest.cc

 // 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.
 
 #include <mojo/bindings/buffer.h>
 
 #include <stdint.h>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "gtest/gtest.h"
 
 namespace {
 
 TEST(MojomBufferTest, RoundTo8) {
   char buffer[100];
   struct MojomBuffer mbuf = {
       buffer, sizeof(buffer),
       0,  // num_bytes_used
   };
 
@@ skipping 23 matching lines @@
 
   // Setup the buffer data so that it will overflow.
   mbuf.num_bytes_used = UINT32_MAX - 7;  // This divides by 8.
   mbuf.buf_size = UINT32_MAX;
 
   // Rounds to 8, and allocates more than it has:
   EXPECT_EQ(NULL, MojomBuffer_Allocate(&mbuf, 1));
 }
 
 }  // namespace