Disable GCM: fail fast PushManager.subscribe() without a token (#3888)

patches/core/ungoogled-chromium/disable-gcm.patch

@@ -154,3 +154,32 @@
  }
  
  std::string GCMClientImpl::GetStateString() const {
+--- a/components/gcm_driver/gcm_driver_desktop.cc
++++ b/components/gcm_driver/gcm_driver_desktop.cc
+@@ -1189,25 +1189,7 @@ GCMClient::Result GCMDriverDesktop::EnsureStarted(
+     GCMClient::StartMode start_mode) {
+   DCHECK(ui_thread_->RunsTasksInCurrentSequence());
+ 
+-  if (gcm_started_)
+-    return GCMClient::SUCCESS;
+-
+-  // Have any app requested the service?
+-  if (app_handlers().empty())
+-    return GCMClient::UNKNOWN_ERROR;
+-
+-  if (!delayed_task_controller_)
+-    delayed_task_controller_ = std::make_unique<GCMDelayedTaskController>();
+-
+-  // Note that we need to pass weak pointer again since the existing weak
+-  // pointer in IOWorker might have been invalidated when GCM is stopped.
+-  io_thread_->PostTask(
+-      FROM_HERE, base::BindOnce(&GCMDriverDesktop::IOWorker::Start,
+-                                base::Unretained(io_worker_.get()), start_mode,
+-                                weak_ptr_factory_.GetWeakPtr(),
+-                                /*time_task_posted=*/base::TimeTicks::Now()));
+-
+-  return GCMClient::SUCCESS;
++  return GCMClient::GCM_DISABLED;
+ }
+ 
+ void GCMDriverDesktop::RemoveCachedData() {