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

ios/chrome/browser/chrome_coordinator.h

 // 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.
 
 #ifndef IOS_CHROME_BROWSER_CHROME_COORDINATOR_H_
 #define IOS_CHROME_BROWSER_CHROME_COORDINATOR_H_
 
 #include <UIKit/UIKit.h>
 
 @class ChromeCoordinator;
 typedef NSMutableArray<ChromeCoordinator*> MutableCoordinatorArray;
 
 // A coordinator object that manages view controllers and other coordinators.
 // Members of this class should clean up their own UI when they are deallocated.
 @interface ChromeCoordinator : NSObject
 
 // Creates a coordinator that will use |viewController|
 - (nullable instancetype)initWithBaseViewController:
     (nullable UIViewController*)viewController NS_DESIGNATED_INITIALIZER;
 
 - (nullable instancetype)init NS_UNAVAILABLE;
 
 // Child coordinators created by this object.
-@property(nonatomic, nonnull, readonly)
+@property(strong, nonatomic, nonnull, readonly)
     MutableCoordinatorArray* childCoordinators;
 
 // The currently 'active' child coordinator, if any. By default this is the last
 // coordinator in |childCoordinators|, but subclasses need not adhere to that.
-@property(nonatomic, nullable, readonly)
+@property(strong, nonatomic, nullable, readonly)
     ChromeCoordinator* activeChildCoordinator;
 
 // The view controller this coordinator was initialized with.
-@property(nonatomic, nullable, readonly) UIViewController* baseViewController;
+@property(weak, nonatomic, nullable, readonly)
+    UIViewController* baseViewController;
 
 // The basic lifecycle methods for coordinators are -start and -stop. These
 // are blank template methods; child classes are expected to implement them and
 // do not need to invoke the superclass methods. Subclasses of ChromeCoordinator
 // that expect to be subclassed should not build functionality into these
 // methods.
 // Starts the user interaction managed by the receiver.
 - (void)start;
 
 // Stops the user interaction managed by the receiver. Called on dealloc.
 - (void)stop;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_CHROME_COORDINATOR_H_