Remove some senseless indirection from the Push API code

Four files to call one Java function. Let's just call it directly.

BUG=

Change-Id: I6e988e9a000051dd7e3dd2b517a33a09afc2fff6
Reviewed-on: https://chromium-review.googlesource.com/749147
Reviewed-by: Anita Woodruff <awdf@chromium.org>
Commit-Queue: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513464}
void PushMessagingServiceImpl::OnSendError(
    const std::string& app_id,
    const gcm::GCMClient::SendErrorDetails& send_error_details) {
  NOTREACHED() << "The Push API shouldn't have sent messages upstream";
}

void PushMessagingServiceImpl::OnSendError(
    const std::string& app_id,
    const gcm::GCMClient::SendErrorDetails& send_error_details) {
  NOTREACHED() << "The Push API shouldn't have sent messages upstream";
}
