Let CRIWVWebView inherit UIView instead of NSObject.

ios/web_view/public/criwv_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_CRIWV_WEB_VIEW_H_
 #define IOS_WEB_VIEW_PUBLIC_CRIWV_WEB_VIEW_H_
 
 #import <UIKit/UIKit.h>
 
 @protocol CRIWVWebViewDelegate;
 
 // Primary objective-c interface for web/.  Just like a WKWebView, but better.

[Eugene But (OOO till 7-30), 2017/02/02 20:54:32]

Do you want to update this comment? This is not an interface for web/ anymore.
Also "better" part is very subjective :). I think the comments should explain
that CRIWVWebView is responsible for rendering web content and in addition to
WKWebView allows Translate, Find In Page and Customizable Context Menus, <maybe
something else?>

[Hiroshi Ichikawa, 2017/02/03 02:14:57]

Done.

 // Concrete instances can be created through CRIWV.
-@protocol CRIWVWebView<NSObject>
+@interface CRIWVWebView : UIView
 
 // The view used to display web content.
 @property(nonatomic, readonly) UIView* view;
 
 // This web view's delegate.
 @property(nonatomic, readwrite, assign) id<CRIWVWebViewDelegate> delegate;
 
 // 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;
 
 // The current page title.
 @property(nonatomic, readonly) NSString* pageTitle;
 
 // The current load progress, as a fraction between 0 and 1.  This value is
 // undefined if the web view is not currently loading.
 @property(nonatomic, readonly) CGFloat loadProgress;
 
+- (instancetype)initWithFrame:(CGRect)frame NS_UNAVAILABLE;
+- (instancetype)initWithCoder:(NSCoder*)aDecoder NS_UNAVAILABLE;
+
 // Navigates backwards or forwards by one page.  Does nothing if the
 // corresponding |canGoBack| or |canGoForward| method returns NO.
 - (void)goBack;
 - (void)goForward;
 
 // Reloads the current page.
 - (void)reload;
 
 // Stops loading the current page.
 - (void)stopLoading;
 
 // Loads the given |url| in this web view.
 - (void)loadURL:(NSURL*)url;
 
 // 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_CRIWV_WEB_VIEW_H_