Fix a crash in MimeHandlerServiceImpl::AbortStream().

extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.cc

 // 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.
 
 #include "extensions/browser/guest_view/mime_handler_view/mime_handler_view_guest.h"
 
 #include "base/strings/stringprintf.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/stream_handle.h"
@@ skipping 21 matching lines @@
                                  int tab_id,
                                  bool embedded,
                                  const GURL& handler_url,
                                  const std::string& extension_id)
     : stream_(stream.Pass()),
       embedded_(embedded),
       tab_id_(tab_id),
       handler_url_(handler_url),
       extension_id_(extension_id),
       weak_factory_(this) {
+  DCHECK(stream_);
 }
 
 StreamContainer::~StreamContainer() {
 }
 
 void StreamContainer::Abort(const base::Closure& callback) {
-  if (!stream_) {
+  if (!stream_->handle) {
     callback.Run();
     return;
   }
   stream_->handle->AddCloseListener(callback);
   stream_->handle.reset();
 }
 
 base::WeakPtr<StreamContainer> StreamContainer::GetWeakPtr() {
   return weak_factory_.GetWeakPtr();
 }
@@ skipping 167 matching lines @@
 
 void MimeHandlerViewGuest::OnRequest(
     const ExtensionHostMsg_Request_Params& params) {
   if (extension_function_dispatcher_) {
     extension_function_dispatcher_->Dispatch(
         params, web_contents()->GetRenderViewHost());
   }
 }
 
 }  // namespace extensions