Add CWVUserContentController which enables injecting JavaScripts.

ios/web_view/internal/cwv_web_view.mm

 // 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.
 
 #import "ios/web_view/public/cwv_web_view.h"
 
 #include <memory>
 #include <utility>
 
 #import "base/ios/weak_nsobject.h"
@@ skipping 36 matching lines @@
 }
 
 // Redefine the property as readwrite to define -setEstimatedProgress:, which
 // can be used to send KVO notification.
 @property(nonatomic, readwrite) double estimatedProgress;
 
 @end
 
 @implementation CWVWebView
 
+@synthesize configuration = _configuration;
 @synthesize navigationDelegate = _navigationDelegate;
 @synthesize translationDelegate = _translationDelegate;
 @synthesize estimatedProgress = _estimatedProgress;
 @synthesize UIDelegate = _UIDelegate;
 
 - (instancetype)initWithFrame:(CGRect)frame
                 configuration:(CWVWebViewConfiguration*)configuration {
   self = [super initWithFrame:frame];
   if (self) {
     _configuration = [configuration copy];
@@ skipping 195 matching lines @@
     [_UIDelegate webViewDidClose:self];
   }
 }
 
 - (web::JavaScriptDialogPresenter*)javaScriptDialogPresenterForWebState:
     (web::WebState*)webState {
   return _javaScriptDialogPresenter.get();
 }
 
 @end