Do nothing on OnSessionStopped if ARC is being restarted.

components/arc/arc_session.cc

Index: components/arc/arc_session.cc
diff --git a/components/arc/arc_session.cc b/components/arc/arc_session.cc
index c063a64574273278a690b13e2d8c49e40426f0a0..4d277d276ece39a3993895c207032511bf2aff2c 100644
--- a/components/arc/arc_session.cc
+++ b/components/arc/arc_session.cc
@@ -600,8 +600,10 @@ void ArcSessionImpl::OnStopped(ArcSessionObserver::StopReason reason) {
   VLOG(2) << "ARC session is stopped.";
   arc_bridge_host_.reset();
   state_ = State::STOPPED;
-  for (auto& observer : observer_list_)
-    observer.OnSessionStopped(reason);
+  for (auto& observer : observer_list_) {
+    // ArcSessionImpl won't restart by itself.
+    observer.OnSessionStopped(reason, false /* restarting */);

[hidehiko, 2017/02/28 16:33:48]

Note: Alternative approach would be splitting ArcSession's Observer and
ArcSessionRunner's Observer.

At the moment, I think it is still ok to share. WDYT?

[Yusuke Sato, 2017/02/28 21:07:17]

I'd actually prefer to split the interface.

* ASM now completely switched to its own observer interface. There seems to be
no reason for ASR to do the same.
* Removing the second parameter makes it clearer that AS never restarts the
instance by itself.
* If you split the observer interface, each interface can have better document
(each interface can mention more things its observers can assume, for example.)

[Yusuke Sato, 2017/02/28 23:13:53]

Sorry there was a typo. I mean, I'd like AS and ASR to use different observer
interfaces.

[hidehiko, 2017/03/01 09:10:05]

So, done.
Split the observer into two: ArcSession::Observer and
ArcSessionRunner::Observer.
To share the StopReason easily, I introduced a new file arc_stop_reason.h.

Note that, if we want to split the dependency between headers, we can define
those observer interfaces in standalone files, e.g. arc_session_observer.h, and
arc_session_runner_observer.h etc. Though, at the moment, it looks not needed,
IMHO, so I defined them as nested class.

+  }
 }
 
 void ArcSessionImpl::OnShutdown() {