Add CWVUIDelegate with method to customize context menu.

ios/web_view/public/cwv_web_view.h

 // Copyright 2014 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_WEB_VIEW_PUBLIC_CWV_WEB_VIEW_H_
 #define IOS_WEB_VIEW_PUBLIC_CWV_WEB_VIEW_H_
 
 #import <UIKit/UIKit.h>
 
 @class CWVWebViewConfiguration;
+@protocol CWVUIDelegate;
 @protocol CWVWebViewDelegate;
 
 // A web view component (like WKWebView) which uses iOS Chromium's web view
 // implementation.
 //
 // In addition to WKWebView features, it allows Translate, Find In Page,
 // Customizable Context Menus, and maybe more.
 //
 // Concrete instances can be created through CWV.
 @interface CWVWebView : UIView
 
 // The view used to display web content.
 @property(nonatomic, readonly) UIView* view;
 
 // This web view's delegate.
 @property(nonatomic, weak) id<CWVWebViewDelegate> delegate;
 
+// This web view's UI delegate
+@property(nonatomic, weak) id<CWVUIDelegate> UIDelegate;

[Eugene But (OOO till 7-30), 2017/02/27 16:34:07]

Feedback for a separate CL: we should probably use nullability annotations for
all WebView headers.

[michaeldo, 2017/02/27 19:02:06]

Agreed, I filed crbug.com/696661

+
 // Whether or not this web view can go backwards or forwards.
 @property(nonatomic, readonly) BOOL canGoBack;
 @property(nonatomic, readonly) BOOL canGoForward;
 
 // Whether or not this web view is loading a page.
 @property(nonatomic, readonly) BOOL isLoading;
 
 // The current URL, for display to the user.
 @property(nonatomic, readonly) NSURL* visibleURL;
 
@@ skipping 28 matching lines @@
 - (void)loadRequest:(NSURLRequest*)request;
 
 // Evaluates a JavaScript string.
 // The completion handler is invoked when script evaluation completes.
 - (void)evaluateJavaScript:(NSString*)javaScriptString
          completionHandler:(void (^)(id, NSError*))completionHandler;
 
 @end
 
 #endif  // IOS_WEB_VIEW_PUBLIC_CWV_WEB_VIEW_H_