[ObjC ARC] Converts ios/chrome/browser/metrics:metrics to ARC.Automatically generated ARCMigrate …

ios/chrome/browser/metrics/previous_session_info.mm

 // Copyright 2015 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/browser/metrics/previous_session_info.h"
 
 #include "base/logging.h"
-#include "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #include "components/version_info/version_info.h"
 #import "ios/chrome/browser/metrics/previous_session_info_private.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 // Key in the NSUserDefaults for a string value that stores the version of the
 // last session.
 NSString* const kLastRanVersion = @"LastRanVersion";
 
 }  // namespace
 
 namespace previous_session_info_constants {
 NSString* const kDidSeeMemoryWarningShortlyBeforeTerminating =
@@ skipping 33 matching lines @@
     NSString* lastRanVersion = [defaults stringForKey:kLastRanVersion];
     NSString* currentVersion =
         base::SysUTF8ToNSString(version_info::GetVersionNumber());
     gSharedInstance.isFirstSessionAfterUpgrade =
         ![lastRanVersion isEqualToString:currentVersion];
   }
   return gSharedInstance;
 }
 
 + (void)resetSharedInstanceForTesting {
-  [gSharedInstance release];
   gSharedInstance = nil;
 }
 
 - (void)beginRecordingCurrentSession {
   if (self.didBeginRecordingCurrentSession)
     return;
   self.didBeginRecordingCurrentSession = YES;
 
   NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
 
@@ skipping 29 matching lines @@
 
   NSUserDefaults* defaults = [NSUserDefaults standardUserDefaults];
   [defaults
       removeObjectForKey:previous_session_info_constants::
                              kDidSeeMemoryWarningShortlyBeforeTerminating];
   // Save critical state information for crash detection.
   [defaults synchronize];
 }
 
 @end