[ios] Added WebState::GetLoadingProgress web// API.

ios/web/web_state/ui/crw_web_controller.mm

 // Copyright 2012 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/web_state/ui/crw_web_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #import <objc/runtime.h>
 #include <stddef.h>
@@ skipping 1840 matching lines @@
 - (id<CRWWebViewProxy>)webViewProxy {
   return _webViewProxy.get();
 }
 
 - (UIView*)viewForPrinting {
   // TODO(ios): crbug.com/227944. Printing is not supported for native
   // controllers.
   return self.webView;
 }
 
+- (double)loadingProgress {
+  return [_webView estimatedProgress];
+}
+
 - (void)registerLoadRequest:(const GURL&)URL {
   // Get the navigation type from the last main frame load request, and try to
   // map that to a PageTransition.
   WKNavigationType navigationType =
       _pendingNavigationInfo ? [_pendingNavigationInfo navigationType]
                              : WKNavigationTypeOther;
   ui::PageTransition transition = ui::PAGE_TRANSITION_CLIENT_REDIRECT;
   switch (navigationType) {
     case WKNavigationTypeLinkActivated:
       transition = ui::PAGE_TRANSITION_LINK;
@@ skipping 3898 matching lines @@
   }
 
   return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 - (NSString*)refererFromNavigationAction:(WKNavigationAction*)action {
   return [action.request valueForHTTPHeaderField:@"Referer"];
 }
 
 @end