[ObjC ARC] Converts ios/chrome/app/safe_mode:unit_tests to ARC.

ios/chrome/app/safe_mode/safe_mode_coordinator_unittest.mm

 // 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.
 
 #import "ios/chrome/app/safe_mode/safe_mode_coordinator.h"
 
 #import <UIKit/UIKit.h>
 
 #include "base/mac/scoped_nsobject.h"
-#include "testing/gtest_mac.h"
+#include "testing/gtest/include/gtest/gtest.h"
 
 TEST(SafeModeCoordinatorTest, RootVC) {
   // Expect that starting a safe mode coordinator will populate the root view
   // controller.
   base::scoped_nsobject<UIWindow> window(
       [[UIWindow alloc] initWithFrame:CGRectMake(0, 0, 100, 100)]);
   EXPECT_TRUE([window rootViewController] == nil);
   base::scoped_nsobject<SafeModeCoordinator> safe_mode_coordinator(
       [[SafeModeCoordinator alloc] initWithWindow:window]);
   [safe_mode_coordinator start];
   EXPECT_FALSE([window rootViewController] == nil);
 }