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

mojo/public/cpp/system/tests/message_pipe_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++ wrappers in mojo/public/cpp/system/message_pipe.h.
 
 #include "mojo/public/cpp/system/message_pipe.h"
 
 #include <vector>
 
+#include "gtest/gtest.h"
 #include "mojo/public/cpp/system/handle.h"
 #include "mojo/public/cpp/system/wait.h"
-#include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
 namespace {
 
 TEST(MessagePipeTest, InvalidArgs) {
   MessagePipeHandle h_invalid;
   EXPECT_FALSE(h_invalid.is_valid());
   EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
             WriteMessageRaw(h_invalid, nullptr, 0, nullptr, 0,
                             MOJO_WRITE_MESSAGE_FLAG_NONE));
@@ skipping 264 matching lines @@
     EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT, MojoClose(h3_value));
 
     EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h2.release().value()));
     EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h0.release().value()));
     EXPECT_EQ(MOJO_RESULT_OK, MojoClose(h1.release().value()));
   }
 }
 
 }  // namespace
 }  // namespace mojo