[ObjC ARC] Converts ios/chrome/app/safe_mode:safe_mode to ARC.

ios/chrome/app/safe_mode/safe_mode_coordinator.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.
 
 #import "ios/chrome/app/safe_mode/safe_mode_coordinator.h"
 
-#include "base/mac/scoped_nsobject.h"
 #import "ios/chrome/app/safe_mode/safe_mode_view_controller.h"
 #include "ios/chrome/browser/crash_loop_detection_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 const int kStartupCrashLoopThreshold = 2;
 }
 
-@interface SafeModeCoordinator ()<SafeModeViewControllerDelegate> {
-  // Weak pointer to window passed on init.
-  base::WeakNSObject<UIWindow> _window;
-  // Weak pointer backing property of the same name.
-  base::WeakNSProtocol<id<SafeModeCoordinatorDelegate>> _delegate;
+@interface SafeModeCoordinator ()<SafeModeViewControllerDelegate>
+@end
+
+@implementation SafeModeCoordinator {
+  __weak UIWindow* _window;
 }
 
-@end
-
-@implementation SafeModeCoordinator
-
-#pragma mark - property implementation.
-
-- (id<SafeModeCoordinatorDelegate>)delegate {
-  return _delegate;
-}
-
-- (void)setDelegate:(id<SafeModeCoordinatorDelegate>)delegate {
-  _delegate.reset(delegate);
-}
+@synthesize delegate = _delegate;
 
 #pragma mark - Public class methods
 
 + (BOOL)shouldStart {
   // Check whether there appears to be a startup crash loop. If not, don't look
   // at anything else.
   if (crash_util::GetFailedStartupAttemptCount() < kStartupCrashLoopThreshold)
     return NO;
 
   return [SafeModeViewController hasSuggestions];
 }
 
 #pragma mark - ChromeCoordinator implementation
 
 - (void)start {
   // Create the SafeModeViewController and make it the root view controller for
   // the window. The window has ownership of it and will dispose of it when
   // another view controller is made root.
   //
   // General note: Safe mode should be safe; it should not depend on other
   // objects being created. Be extremely conservative when adding code to this
   // method.
-  base::scoped_nsobject<SafeModeViewController> viewController(
-      [[SafeModeViewController alloc] initWithDelegate:self]);
+  SafeModeViewController* viewController =
+      [[SafeModeViewController alloc] initWithDelegate:self];
   [self.window setRootViewController:viewController];
 
   // Reset the crash count; the user may change something based on the recovery
   // UI that will fix the crash, and having the next launch start in recovery
   // mode would be strange.
   crash_util::ResetFailedStartupAttemptCount();
 }
 
 // Override of ChildCoordinators method, which is not supported in this class.
 - (MutableCoordinatorArray*)childCoordinators {
   NOTREACHED() << "Do not add child coordinators to SafeModeCoordinator.";
   return nil;
 }
 
 #pragma mark - SafeModeViewControllerDelegate implementation
 
 - (void)startBrowserFromSafeMode {
   [self.delegate coordinatorDidExitSafeMode:self];
 }
 
 @end