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

mojo/public/cpp/environment/tests/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("../../../mojo_sdk.gni")
 
 mojo_sdk_source_set("tests") {
   testonly = true
 
   sources = [
     "async_wait_unittest.cc",
     "async_waiter_unittest.cc",
     "logger_unittest.cc",
     "logging_unittest.cc",
   ]
 
-  deps = [
-    "//testing/gtest",
-  ]
-
   mojo_sdk_deps = [
+    "mojo/public:gtest",
     "mojo/public/c:environment",
     "mojo/public/cpp/bindings:callback",
     "mojo/public/cpp/environment:standalone",
     "mojo/public/cpp/system",
     "mojo/public/cpp/test_support:test_utils",
     "mojo/public/cpp/utility",
   ]
 }
 
 mojo_sdk_source_set("perftests") {
   testonly = true
 
   sources = [
     "run_loop_async_wait_perftest.cc",
   ]
 
-  deps = [
-    "//testing/gtest",
-  ]
-
   mojo_sdk_deps = [
+    "mojo/public:gtest",
     "mojo/public/c:environment_perftest_helpers",
     "mojo/public/cpp/environment:standalone",
     "mojo/public/cpp/system",
     "mojo/public/cpp/test_support",
     "mojo/public/cpp/utility",
   ]
 }