Get FileSelect dialog work on athena

athena/content/app_activity_proxy.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 "athena/content/app_activity_proxy.h"
 
 #include "athena/content/app_activity.h"
 #include "athena/content/app_activity_registry.h"
 #include "athena/wm/public/window_list_provider.h"
 #include "athena/wm/public/window_manager.h"
@@ skipping 39 matching lines @@
 
 Activity::ActivityMediaState AppActivityProxy::GetMediaState() {
   // This proxy has never any media playing.
   return ACTIVITY_MEDIA_STATE_NONE;
 }
 
 aura::Window* AppActivityProxy::GetWindow() {
   return view_->GetWidget()->GetNativeWindow();
 }
 
+content::WebContents* AppActivityProxy::GetWebContents() {
+  return NULL;
+}
+
 void AppActivityProxy::Init() {
   DCHECK(replaced_activity_);
   // Get the content proxy to present the content.
   content_proxy_ = replaced_activity_->GetContentProxy(GetWindow());
   WindowListProvider* window_list_provider =
       WindowManager::Get()->GetWindowListProvider();
   window_list_provider->StackWindowBehindTo(GetWindow(),
                                             replaced_activity_->GetWindow());
   // Creating this object was moving the activation to this window which should
   // not be the active window. As such we re-activate the top activity window.
@@ skipping 32 matching lines @@
   return content_proxy_->GetContentImage();
 }
 
 void AppActivityProxy::PrepareContentsForOverview() {
 }
 
 void AppActivityProxy::ResetContentsView() {
 }
 
 }  // namespace athena