arc: Notify ARC instance failures via callbacks.

components/arc/arc_bridge_bootstrap.h

Index: components/arc/arc_bridge_bootstrap.h
diff --git a/components/arc/arc_bridge_bootstrap.h b/components/arc/arc_bridge_bootstrap.h
index 918c2c0bba838a31e4fa36bc55ae9c825c10e2c5..08fb39787cae666d33ab7f17ee4bfb8717a78879 100644
--- a/components/arc/arc_bridge_bootstrap.h
+++ b/components/arc/arc_bridge_bootstrap.h
@@ -10,6 +10,7 @@
 #include "base/macros.h"
 #include "base/sequenced_task_runner.h"
 #include "base/single_thread_task_runner.h"
+#include "components/arc/arc_bridge_service.h"
 #include "components/arc/common/arc_bridge.mojom.h"
 
 namespace arc {
@@ -19,11 +20,16 @@ namespace arc {
 // being available.
 class ArcBridgeBootstrap {
  public:
+  using StopReason = ArcBridgeService::StopReason;
+
   class Delegate {
    public:
+    // Called when the connection with ARC instance has been established.
     virtual void OnConnectionEstablished(
         mojom::ArcBridgeInstancePtr instance_ptr) = 0;
-    virtual void OnStopped() = 0;
+
+    // Called when ARC instance is stopped.
+    virtual void OnStopped(StopReason reason) = 0;
   };
 
   // Creates a default instance of ArcBridgeBootstrap.