Let CRIWVWebView inherit UIView instead of NSObject.

ios/web_view/public/criwv.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_H_
 #define IOS_WEB_VIEW_PUBLIC_CRIWV_H_
 
+#import <CoreGraphics/CoreGraphics.h>
 #import <Foundation/Foundation.h>
 
 @protocol CRIWVDelegate;
-@protocol CRIWVWebView;
+@class CRIWVWebView;
 
 // Main interface for the CRIWV library.
 __attribute__((visibility("default")))
 @interface CRIWV : NSObject
 
 // Initializes the CRIWV library.  This function should be called from
 // |application:didFinishLaunchingWithOptions:|.
 + (void)configureWithDelegate:(id<CRIWVDelegate>)delegate;
 
 // Shuts down the CRIWV library.  This function should be called from
 // |applicationwillTerminate:|.
 + (void)shutDown;
 
 // Creates and returns a web view.
-+ (id<CRIWVWebView>)webView;
++ (CRIWVWebView*)webViewWithFrame:(CGRect)frame;
 
 @end
 
 #endif  // IOS_WEB_VIEW_PUBLIC_CRIWV_H_