This patch enables "mailto" links in WebViews.

chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.cc

 // Copyright (c) 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.
 
 #include "chrome/browser/renderer_host/chrome_resource_dispatcher_host_delegate.h"
 
 #include <string>
 #include <vector>
 
 #include "base/base64.h"
@@ skipping 493 matching lines @@
 }
 
 bool ChromeResourceDispatcherHostDelegate::HandleExternalProtocol(
     const GURL& url,
     int child_id,
     int route_id,
     bool is_main_frame,
     ui::PageTransition page_transition,
     bool has_user_gesture) {
 #if defined(ENABLE_EXTENSIONS)
-  if (extensions::WebViewRendererState::GetInstance()->IsGuest(child_id))
+  // External protocols are disabled for guests. An exception is made for the
+  // "mailto" protocol, so that pages that utilize it work properly in a
+  // WebView.
+  if (extensions::WebViewRendererState::GetInstance()->IsGuest(child_id) &&
+      !url.SchemeIs(url::kMailToScheme)) {
     return false;
+  }
 #endif  // defined(ENABLE_EXTENSIONS)
 
 #if defined(OS_ANDROID)
   // Main frame external protocols are handled by
   // InterceptNavigationResourceThrottle.
   if (is_main_frame)
     return false;
 #endif  // defined(ANDROID)
 
   BrowserThread::PostTask(
@@ skipping 241 matching lines @@
                                        url_request->GetTotalReceivedBytes()));
   }
 }
 
 // static
 void ChromeResourceDispatcherHostDelegate::
     SetExternalProtocolHandlerDelegateForTesting(
     ExternalProtocolHandler::Delegate* delegate) {
   g_external_protocol_handler_delegate = delegate;
 }