arc: Only call StopVm() if ARCVM is running

This change adds a check in ArcVmClientAdapter::StopArcInstance() to see
if a VM is running (current_cid_ is set). If not, skip calling
ConciergeClient::StopVm() and notify observers that ARCVM is stopped
right away.

BUG=b:169893632
TEST=arc.AuthPerf.unmanaged_vm

Change-Id: Ic927f122cacea0e89cacffbbcd67a217772dba43
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2462573
Commit-Queue: Willie Koomson <wvk@google.com>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816221}

components/arc/session/arc_vm_client_adapter.cc

@@ -547,6 +547,13 @@ class ArcVmClientAdapter : public ArcClientAdapter,
           << "StopArcInstance is called during browser shutdown. Do nothing.";
       return;
     }
+    if (current_cid_ == kInvalidCid) {
+      // No VM is currently running, avoid calling ConciergeClient::StopVm().
+      // TODO(wvk): Once StartMiniArc() is implemented, use a DCHECK here
+      // instead.
+      OnArcInstanceStopped();
+      return;
+    }
 
     if (should_backup_log) {
       GetDebugDaemonClient()->BackupArcBugReport(