[iOS Reading List] Only allow offline URL when the offline file exists.

ios/chrome/browser/ui/browser_view_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/chrome/browser/ui/browser_view_controller.h"
 
 #import <AssetsLibrary/AssetsLibrary.h>
 #import <MobileCoreServices/MobileCoreServices.h>
 #import <PassKit/PassKit.h>
 #import <Photos/Photos.h>
@@ skipping 2952 matching lines @@
                                             url:url
                                           error:error
                                          isPost:isPost
                                     isIncognito:_isOffTheRecord] autorelease];
   [self setOverScrollActionControllerToStaticNativeContent:errorPageContent];
   return errorPageContent;
 }
 
 - (BOOL)hasControllerForURL:(const GURL&)url {
   std::string host(url.host());
+  if (host == kChromeUIOfflineHost) {
+    // Only allow offline URL that are fully specified.
+    return reading_list::IsOfflineURLValid(
+        url, ReadingListModelFactory::GetForBrowserState(_browserState));
+  }
 
   return host == kChromeUINewTabHost || host == kChromeUIBookmarksHost ||
-         host == kChromeUITermsHost || host == kChromeUIOfflineHost;
+         host == kChromeUITermsHost;
 }
 
 - (id<CRWNativeContent>)controllerForURL:(const GURL&)url
                                 webState:(web::WebState*)webState {
   DCHECK(url.SchemeIs(kChromeUIScheme));
 
   id<CRWNativeContent> nativeController = nil;
   std::string url_host = url.host();
   if (url_host == kChromeUINewTabHost || url_host == kChromeUIBookmarksHost) {
     NewTabPageController* pageController =
@@ skipping 32 matching lines @@
 
     StaticHtmlNativeContent* staticNativeController =
         [[[StaticHtmlNativeContent alloc]
             initWithResourcePathResource:base::SysUTF8ToNSString(filename)
                                   loader:self
                             browserState:_browserState
                                      url:GURL(kChromeUITermsURL)] autorelease];
     [self setOverScrollActionControllerToStaticNativeContent:
               staticNativeController];
     nativeController = staticNativeController;
-  } else if (url_host == kChromeUIOfflineHost) {
+  } else if (url_host == kChromeUIOfflineHost &&
+             [self hasControllerForURL:url]) {
     StaticHtmlNativeContent* staticNativeController =
         [[[OfflinePageNativeContent alloc] initWithLoader:self
                                              browserState:_browserState
                                                  webState:webState
                                                       URL:url] autorelease];
     [self setOverScrollActionControllerToStaticNativeContent:
               staticNativeController];
     nativeController = staticNativeController;
   } else if (url_host == kChromeUIExternalFileHost) {
     // Return an instance of the |ExternalFileController| only if the file is
@@ skipping 2085 matching lines @@
 
 - (UIView*)voiceSearchButton {
   return _voiceSearchButton;
 }
 
 - (id<LogoAnimationControllerOwner>)logoAnimationControllerOwner {
   return [self currentLogoAnimationControllerOwner];
 }
 
 @end