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

ios/chrome/browser/metrics/tab_usage_recorder_unittest.mm

Index: ios/chrome/browser/metrics/tab_usage_recorder_unittest.mm
diff --git a/ios/chrome/browser/metrics/tab_usage_recorder_unittest.mm b/ios/chrome/browser/metrics/tab_usage_recorder_unittest.mm
index ccd9cd22ef5268bb9835885960e0f468c8e49f41..ca0817bb3b7d0c7201b6f0f7c9e7959367255ad4 100644
--- a/ios/chrome/browser/metrics/tab_usage_recorder_unittest.mm
+++ b/ios/chrome/browser/metrics/tab_usage_recorder_unittest.mm
@@ -4,7 +4,6 @@
 
 #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"
@@ -20,6 +19,10 @@
 #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;
 }
@@ -105,7 +108,7 @@ class TabUsageRecorderTest : public PlatformTest {
     [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_;
@@ -312,8 +315,8 @@ 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);