[ObjC ARC] Converts ios/chrome/browser/metrics:unit_tests_internal to ARC.

ios/chrome/browser/metrics/tab_usage_recorder_unittest.mm

 // Copyright 2013 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 <memory>
 
-#include "base/mac/scoped_nsobject.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram_samples.h"
 #include "base/stl_util.h"
 #include "base/test/histogram_tester.h"
 #import "ios/chrome/browser/metrics/previous_session_info.h"
 #include "ios/chrome/browser/metrics/tab_usage_recorder.h"
 #import "ios/chrome/browser/metrics/tab_usage_recorder_delegate.h"
 #import "ios/chrome/browser/tabs/tab.h"
 #include "ios/testing/ocmock_complex_type_helper.h"
 #include "ios/web/public/test/test_web_thread.h"
 #import "ios/web/web_state/ui/crw_web_controller.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/platform_test.h"
 #include "third_party/ocmock/ocmock_extensions.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @interface TURTestTabMock : OCMockComplexTypeHelper {
   GURL _url;
 }
 
 @property(nonatomic, assign) const GURL& url;
 @end
 
 @implementation TURTestTabMock
 - (const GURL&)url {
   return _url;
@@ skipping 65 matching lines @@
   id MockTab(bool inMemory) {
     id tab_mock = [[TURTestTabMock alloc]
         initWithRepresentedObject:[OCMockObject mockForClass:[Tab class]]];
     id web_controller_mock =
         [OCMockObject mockForClass:[CRWWebController class]];
     [[[tab_mock stub] andReturn:web_controller_mock] webController];
     [[[tab_mock stub] andReturnBool:false] isPrerenderTab];
     [tab_mock setUrl:webUrl_];
     [[[web_controller_mock stub] andReturnBool:inMemory] isViewAlive];
     [[web_controller_mock stub] removeObserver:OCMOCK_ANY];
-    return [tab_mock autorelease];
+    return tab_mock;
   }
 
   GURL webUrl_;
   GURL nativeUrl_;
   std::unique_ptr<base::MessageLoop> loop_;
   std::unique_ptr<web::TestWebThread> ui_thread_;
   std::unique_ptr<base::HistogramTester> histogram_tester_;
   std::unique_ptr<TabUsageRecorderForTesting> tab_usage_recorder_;
 };
 
@@ skipping 186 matching lines @@
   // Should record nothing.
   tab_usage_recorder_->RecordPageLoadStart(tab_mock_b);
   histogram_tester_->ExpectTotalCount(kTimeAfterLastRestore, 1);
 }
 
 // Verifies that metrics are recorded correctly when a renderer terminates.
 TEST_F(TabUsageRecorderTest, RendererTerminated) {
   Tab* terminated_tab = MockTab(false);
 
   // Set up the delegate to return |kAliveTabsCountAtRenderTermination|.
-  base::scoped_nsobject<MockTabUsageRecorderDelegate> delegate(
-      [[MockTabUsageRecorderDelegate alloc] init]);
+  MockTabUsageRecorderDelegate* delegate =
+      [[MockTabUsageRecorderDelegate alloc] init];
   [delegate setLiveTabsCount:kAliveTabsCountAtRendererTermination];
   tab_usage_recorder_->SetDelegate(delegate);
 
   base::TimeTicks now = base::TimeTicks::Now();
 
   // Add |kExpiredTimesAddedCount| expired timestamps and one recent timestamp
   // to the termination timestamp list.
   for (int seconds = kExpiredTimesAddedCount; seconds > 0; seconds--) {
     int expired_time_delta = kSecondsBeforeRendererTermination + seconds;
     tab_usage_recorder_->AddTimeToDeque(
@@ skipping 30 matching lines @@
 
   tab_usage_recorder_->RendererTerminated(tab_mock_b, false);
   tab_usage_recorder_->RecordTabSwitched(tab_mock_a, tab_mock_b);
 
   histogram_tester_->ExpectUniqueSample(
       kSelectedTabHistogramName,
       TabUsageRecorder::EVICTED_DUE_TO_RENDERER_TERMINATION, 1);
 }
 
 }  // namespace