Let CRIWVWebView inherit UIView instead of NSObject.

ios/web_view/public/criwv_web_view_delegate.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_DELEGATE_H_
 #define IOS_WEB_VIEW_PUBLIC_CRIWV_WEB_VIEW_DELEGATE_H_
 
 #import <Foundation/Foundation.h>
 
 @protocol CRIWVTranslateDelegate;
-@protocol CRIWVWebView;
+@class CRIWVWebView;
 
 typedef NS_OPTIONS(NSUInteger, CRIWVWebViewUpdateType) {
   CRIWVWebViewUpdateTypeProgress = 1 << 0,
   CRIWVWebViewUpdateTypeTitle = 1 << 1,
   CRIWVWebViewUpdateTypeURL = 1 << 2
 };
 
 // Delegate protocol for CRIWVWebViews.  Allows embedders to customize web view
 // behavior and receive updates on page load progress.
 @protocol CRIWVWebViewDelegate<NSObject>
 
 @optional
 
-- (void)webView:(id<CRIWVWebView>)webView
+- (void)webView:(CRIWVWebView*)webView
     didFinishLoadingWithURL:(NSURL*)url
                 loadSuccess:(BOOL)loadSuccess;
 
-- (void)webView:(id<CRIWVWebView>)webView
+- (void)webView:(CRIWVWebView*)webView
     didUpdateWithChanges:(CRIWVWebViewUpdateType)changes;
 
 - (id<CRIWVTranslateDelegate>)translateDelegate;
 
 @end
 
 #endif  // IOS_WEB_VIEW_PUBLIC_CRIWV_WEB_VIEW_DELEGATE_H_