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

ios/chrome/browser/ui/browser_view_controller.h

Index: ios/chrome/browser/ui/browser_view_controller.h
diff --git a/ios/chrome/browser/ui/browser_view_controller.h b/ios/chrome/browser/ui/browser_view_controller.h
index 4b004dd150465132e623ece475fc0fd4b5a1d6bb..2870f45c4815db344224d9442aabda8836fc86a1 100644
--- a/ios/chrome/browser/ui/browser_view_controller.h
+++ b/ios/chrome/browser/ui/browser_view_controller.h
@@ -72,10 +72,10 @@ extern NSString* const kLocationBarResignsFirstResponderNotification;
 - (instancetype)initWithCoder:(NSCoder*)aDecoder NS_UNAVAILABLE;
 
 // The top-level browser container view.
-@property(nonatomic, retain) BrowserContainerView* contentArea;
+@property(nonatomic, strong) BrowserContainerView* contentArea;
 
 // Invisible button used to dismiss the keyboard.
-@property(nonatomic, retain) UIButton* typingShield;
+@property(nonatomic, strong) UIButton* typingShield;
 
 // Activates/deactivates the object. This will enable/disable the ability for
 // this object to browse, and to have live UIWebViews associated with it. While
@@ -87,7 +87,7 @@ extern NSString* const kLocationBarResignsFirstResponderNotification;
 @property(nonatomic, assign, readonly, getter=isPlayingTTS) BOOL playingTTS;
 
 // Returns the TabModel passed to the initializer.
-@property(nonatomic, assign, readonly) TabModel* tabModel;
+@property(nonatomic, weak, readonly) TabModel* tabModel;
 
 // Returns the ios::ChromeBrowserState passed to the initializer.
 @property(nonatomic, assign, readonly) ios::ChromeBrowserState* browserState;