Reland of [ObjC ARC] Converts ios/chrome/browser/ui/contextual_search:contextual_search to ARC.

ios/chrome/browser/ui/contextual_search/contextual_search_controller.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_CONTEXTUAL_SEARCH_CONTEXTUAL_SEARCH_CONTROLLER_H_
 #define IOS_CHROME_BROWSER_UI_CONTEXTUAL_SEARCH_CONTEXTUAL_SEARCH_CONTROLLER_H_
 
 #import <UIKit/UIKit.h>
 
 #include "base/ios/block_types.h"
@@ skipping 74 matching lines @@
 // Only tests should set this directly; for general use, use -setTab:, which
 // will set this property with the tab's webState.
 @property(nonatomic, assign) web::WebState* webState;
 
 // The panel view that this controller should populate with subviews and use.
 // Owned by its superview. Setting this will have the controller create subviews
 // for the panel; code that sets this property is responsible for disposing of
 // the old panel and its views.
 // This property can only be assigned a non-nil value, and can only be assigned
 // a value when its current value is nil.
-@property(nonatomic, assign) ContextualSearchPanelView* panel;
+@property(nonatomic, weak) ContextualSearchPanelView* panel;
 
 // Designated initializer.
 - (instancetype)initWithBrowserState:(ios::ChromeBrowserState*)browserState
                             delegate:(id<ContextualSearchControllerDelegate>)
                                          delegate;
 
 // Set the Tab to be used as the opener for the search results tab. |opener|'s
 // lifetime should be greater than the receiver's. |opener| can be nil.
 - (void)setTab:(Tab*)tab;
 
@@ skipping 13 matching lines @@
 @end
 
 // Testing category that allows a permissions class to be injected.
 @interface ContextualSearchController (Testing)
 
 - (void)setPermissions:(TouchToSearchPermissionsMediator*)permissions;
 
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_CONTEXTUAL_SEARCH_CONTEXTUAL_SEARCH_CONTROLLER_H_