Fix crash in PPB_FileChooser_Dev proxy.

ppapi/proxy/ppb_file_chooser_proxy.cc

 // Copyright (c) 2011 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 "ppapi/proxy/ppb_file_chooser_proxy.h"
 
 #include <queue>
 
 #include "base/bind.h"
 #include "ppapi/c/dev/ppb_file_chooser_dev.h"
@@ skipping 107 matching lines @@
 
   if (current_show_callback_.func)
     return PP_ERROR_INPROGRESS;  // Can't show more than once.
 
   current_show_callback_ = callback;
   PluginDispatcher::GetForResource(this)->Send(
       new PpapiHostMsg_PPBFileChooser_Show(
           INTERFACE_ID_PPB_FILE_CHOOSER,
           host_resource(),
           save_as,
-          suggested_file_name,
+          suggested_file_name ? suggested_file_name : "",
           require_user_gesture));
   return PP_OK_COMPLETIONPENDING;
 }
 
 PP_Resource FileChooser::GetNextChosenFile() {
   if (file_queue_.empty())
     return 0;
 
   // Return the next resource in the queue. These resource have already been
   // addrefed (they're currently owned by the FileChooser) and returning them
@@ skipping 45 matching lines @@
     PP_FileChooserMode_Dev mode,
     const char* accept_mime_types) {
   Dispatcher* dispatcher = PluginDispatcher::GetForInstance(instance);
   if (!dispatcher)
     return 0;
 
   HostResource result;
   dispatcher->Send(new PpapiHostMsg_PPBFileChooser_Create(
       INTERFACE_ID_PPB_FILE_CHOOSER, instance,
       mode,
-      accept_mime_types,
+      accept_mime_types ? accept_mime_types : "",
       &result));
 
   if (result.is_null())
     return 0;
   return (new FileChooser(result))->GetReference();
 }
 
 bool PPB_FileChooser_Proxy::OnMessageReceived(const IPC::Message& msg) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(PPB_FileChooser_Proxy, msg)
@@ skipping 71 matching lines @@
       files.push_back(cur_create_info);
     }
   }
 
   dispatcher()->Send(new PpapiMsg_PPBFileChooser_ChooseComplete(
       INTERFACE_ID_PPB_FILE_CHOOSER, chooser, result, files));
 }
 
 }  // namespace proxy
 }  // namespace ppapi