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

ios/chrome/browser/metrics/previous_session_info.mm

Index: ios/chrome/browser/metrics/previous_session_info.mm
diff --git a/ios/chrome/browser/metrics/previous_session_info.mm b/ios/chrome/browser/metrics/previous_session_info.mm
index e435eaee65f2e0f18337df20575319ec5b7c5f85..30c4c4f1a42c08f14295caa387f67b91b98be3b0 100644
--- a/ios/chrome/browser/metrics/previous_session_info.mm
+++ b/ios/chrome/browser/metrics/previous_session_info.mm
@@ -5,11 +5,14 @@
 #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
@@ -63,7 +66,6 @@ static PreviousSessionInfo* gSharedInstance = nil;
 }
 
 + (void)resetSharedInstanceForTesting {
-  [gSharedInstance release];
   gSharedInstance = nil;
 }