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

ios/chrome/browser/ui/tab_switcher/tab_switcher_header_view.h

 // 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.
 
 #ifndef IOS_CHROME_BROWSER_UI_TAB_SWITCHER_TAB_SWITCHER_HEADER_VIEW_H_
 #define IOS_CHROME_BROWSER_UI_TAB_SWITCHER_TAB_SWITCHER_HEADER_VIEW_H_
 
 #import <UIKit/UIKit.h>
 
 #include "base/ios/block_types.h"
@@ skipping 13 matching lines @@
 
 @protocol TabSwitcherHeaderViewDataSource<NSObject>
 
 - (NSInteger)tabSwitcherHeaderViewSessionCount;
 - (TabSwitcherSessionCellData*)sessionCellDataAtIndex:(NSUInteger)index;
 
 @end
 
 @interface TabSwitcherHeaderView : UIView
 
-@property(nonatomic, assign) id<TabSwitcherHeaderViewDelegate> delegate;
-@property(nonatomic, assign) id<TabSwitcherHeaderViewDataSource> dataSource;
-@property(nonatomic, readonly) UIView* dismissButton;
+@property(nonatomic, weak) id<TabSwitcherHeaderViewDelegate> delegate;
+@property(nonatomic, weak) id<TabSwitcherHeaderViewDataSource> dataSource;
+@property(weak, nonatomic, readonly) UIView* dismissButton;
 
 // Selects the item at the specified index.
 // The delegate is not called.
 - (void)selectItemAtIndex:(NSInteger)index;
 
 // Reload the collection view.
 - (void)reloadData;
 
 // Performs an update on the header view using the passed block.
 - (void)performUpdate:(void (^)(TabSwitcherHeaderView* headerView))updateBlock;
 
 // Performs an update on the header view using the passed block, the completion
 // handler block is called at the end of the update animations.
 - (void)performUpdate:(void (^)(TabSwitcherHeaderView* headerView))updateBlock
            completion:(ProceduralBlock)completion;
 
 // Updates methods can only be called inside an update block passed to the
 // - (void)performUpdate: method.
 // Update methods takes arrays of NSNumbers.
 - (void)insertSessionsAtIndexes:(NSArray*)indexes;
 - (void)removeSessionsAtIndexes:(NSArray*)indexes;
 
 // Returns the accessibility title of the panel at index |index|.
 - (NSString*)panelTitleAtIndex:(NSInteger)index;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_TAB_SWITCHER_TAB_SWITCHER_HEADER_VIEW_H_