Maintain a map of all resources in the resource tracker and clear instance back pointers when needed,

BUG=85808
Review URL: http://codereview.chromium.org/7196001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@89746 0039d316-1c4b-4281-b951-d872f2087c98
int32_t PPB_URLLoader_Impl::ValidateCallback(PP_CompletionCallback callback) {
  if (!callback.func)
    return PP_ERROR_BADARGUMENT;

  if (pending_callback_.get() && !pending_callback_->completed())
    return PP_ERROR_INPROGRESS;

  return PP_OK;
}

int32_t PPB_URLLoader_Impl::ValidateCallback(PP_CompletionCallback callback) {
  if (!callback.func)
    return PP_ERROR_BADARGUMENT;

  if (pending_callback_.get() && !pending_callback_->completed())
    return PP_ERROR_INPROGRESS;

  return PP_OK;
}
