[iOS Clean] Wired up ContextMenuCommands.

ios/clean/chrome/browser/ui/context_menu/context_menu_view_controller.mm

 // Copyright 2017 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/clean/chrome/browser/ui/context_menu/context_menu_view_controller.h"
 
+#import "ios/clean/chrome/browser/ui/commands/context_menu_commands.h"
+
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 namespace {
 // Typedef the block parameter for UIAlertAction for readability.
 typedef void (^AlertActionHandler)(UIAlertAction*);
 }
 
 @interface ContextMenuViewController ()
 // Object to which command messages will be sent.
 @property(nonatomic, weak) id dispatcher;
 @end
 
 @implementation ContextMenuViewController
 @synthesize dispatcher = _dispatcher;
 
-- (instancetype)initWithDispatcher:(id)dispatcher {
+- (instancetype)initWithDispatcher:(id<ContextMenuCommands>)dispatcher {
   self =
       [[self class] alertControllerWithTitle:nil
                                      message:nil
                               preferredStyle:UIAlertControllerStyleActionSheet];
   if (self) {
     _dispatcher = dispatcher;
   }
   return self;
 }
 
 #pragma mark - ContextMenuConsumer
 
 - (void)setContextMenuTitle:(NSString*)title {
   self.title = title;
 }
 
 - (void)setContextMenuItems:(NSArray<ContextMenuItem*>*)items {
   for (ContextMenuItem* item in items) {
     // Create a block that sends the invocation passed in with the item's
     // configuration to the dispatcher.
     AlertActionHandler handler = ^(UIAlertAction* action) {
       [item.command invokeWithTarget:self.dispatcher];
     };
     [self addAction:[UIAlertAction actionWithTitle:item.title
                                              style:UIAlertActionStyleDefault
                                            handler:handler]];
   }
 
   // Always add a cancel action.
+  AlertActionHandler cancelHandler = ^(UIAlertAction* action) {
+    [self.dispatcher cancelContextMenu];
+  };
   [self addAction:[UIAlertAction actionWithTitle:@"Cancel"
                                            style:UIAlertActionStyleCancel
-                                         handler:nil]];
+                                         handler:cancelHandler]];
 }
 
 @end