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

mojo/public/c/tests/system/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.
 
 // This file tests the C buffer API (the functions declared in
 // mojo/public/c/include/mojo/system/buffer.h).
 
 #include <mojo/system/buffer.h>
 
 #include <mojo/result.h>
 #include <mojo/system/handle.h>
 
-#include "testing/gtest/include/gtest/gtest.h"
+#include "gtest/gtest.h"
 
 namespace {
 
 const MojoHandleRights kDefaultSharedBufferHandleRights =
     MOJO_HANDLE_RIGHT_DUPLICATE | MOJO_HANDLE_RIGHT_TRANSFER |
     MOJO_HANDLE_RIGHT_GET_OPTIONS | MOJO_HANDLE_RIGHT_SET_OPTIONS |
     MOJO_HANDLE_RIGHT_MAP_READABLE | MOJO_HANDLE_RIGHT_MAP_WRITABLE |
     MOJO_HANDLE_RIGHT_MAP_EXECUTABLE;
 
 // The only handle that's guaranteed to be invalid is |MOJO_HANDLE_INVALID|.
@@ skipping 99 matching lines @@
   EXPECT_EQ(MOJO_RESULT_PERMISSION_DENIED, MojoDuplicateHandle(h2, &h3));
   EXPECT_EQ(MOJO_HANDLE_INVALID, h3);
 
   EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h1));
   EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h2));
 }
 
 // TODO(vtl): Add multi-threaded tests.
 
 }  // namespace