[ObjC ARC] Converts ios/web:web to ARC.

ios/web/public/test/web_test.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.
 
 #include "ios/web/public/test/web_test.h"
 
 #include "base/memory/ptr_util.h"
 #include "ios/web/public/active_state_manager.h"
 #include "ios/web/public/web_state/global_web_state_observer.h"
 #import "ios/web/public/test/fakes/test_web_client.h"
@@ skipping 10 matching lines @@
   }
 };
 
 WebTest::WebTest()
     : web_client_(base::WrapUnique(new TestWebClient)),
       crash_observer_(base::MakeUnique<WebTestRenderProcessCrashObserver>()) {}
 
 WebTest::~WebTest() {}
 
 void WebTest::SetUp() {
+  root_pool_ = [[NSAutoreleasePool alloc] init];
   PlatformTest::SetUp();
   BrowserState::GetActiveStateManager(&browser_state_)->SetActive(true);
 }
 
 void WebTest::TearDown() {
   BrowserState::GetActiveStateManager(&browser_state_)->SetActive(false);
   PlatformTest::TearDown();
+  [root_pool_ release];
+  root_pool_ = nil;
 }
 
 TestWebClient* WebTest::GetWebClient() {
   return static_cast<TestWebClient*>(web_client_.Get());
 }
 
 BrowserState* WebTest::GetBrowserState() {
   return &browser_state_;
 }
 
 void WebTest::SetIgnoreRenderProcessCrashesDuringTesting(bool allow) {
   if (allow) {
     crash_observer_ = nullptr;
   } else {
     crash_observer_ = base::MakeUnique<WebTestRenderProcessCrashObserver>();
   }
 }
 
 }  // namespace web