arc: Notify ARC instance failures via callbacks.

components/arc/arc_bridge_bootstrap.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_ARC_ARC_BRIDGE_BOOTSTRAP_H_
 #define COMPONENTS_ARC_ARC_BRIDGE_BOOTSTRAP_H_
 
 #include <memory>
 
 #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 {
 
 // Starts the ARC instance and bootstraps the bridge connection.
 // Clients should implement the Delegate to be notified upon communications
 // being available.
 class ArcBridgeBootstrap {
  public:
+  using AbortReason = ArcBridgeService::AbortReason;
+
   class Delegate {
    public:
+    // Called when a connection with ARC instance has been established.

[Luis Héctor Chávez, 2016/07/08 18:01:02]

nit: when the connection

[Shuhei Takahashi, 2016/07/11 08:25:19]

Done.

     virtual void OnConnectionEstablished(
         mojom::ArcBridgeInstancePtr instance_ptr) = 0;
+
+    // Called when ARC instance is being aborted due to errors.
+    // This can happen if it has failed to boot, or it has crashed after boot.
+    // After this callback is invoked, the ARC instance will be stopped, so
+    // you do not need to call ArcBridgeBootstrap::Stop() in the callback.
+    // Note: This callback can be called multiple times before OnStopped() if
+    // we encounter multiple errors during the process.
+    virtual void OnAborting(AbortReason reason) = 0;
+
+    // Called when ARC instance has stopped.
+    // When the ARC instance is being aborted due to errors, OnAborting() is
+    // called first, then OnStopped() is called once the instance is stopped.
     virtual void OnStopped() = 0;

[Luis Héctor Chávez, 2016/07/08 18:01:02]

Do you have an example of an instance where OnAborting() would need to be called
more than once before calling OnStopped()? Is there any way we can avoid that?

I think I'd prefer to have only OnStopped() with a StopReason parameter (where
it can be BOOT_FAILURE, CRASH, or CLEAN_TERMINATION). At least that way the
opt-in flow can have a slightly simpler implementation.

[Shuhei Takahashi, 2016/07/11 08:25:19]

It is possible ArcBridgeBootstrap encounters multiple errors. For example, both
ArcBridgeBootstrapImpl::AcceptInstanceConnection() failure and ARC container
crash can happen at the same time.

Anyway, I agree adding StopReason parameter to OnStopped() is easier to use from
callers. I've updated the patch to add a OnStopped()/OnBridgeStopped()
parameter, instead of adding a new observer method.

   };
 
   // Creates a default instance of ArcBridgeBootstrap.
   static std::unique_ptr<ArcBridgeBootstrap> Create();
   virtual ~ArcBridgeBootstrap() = default;
 
   // This must be called before calling Start() or Stop(). |delegate| is owned
   // by the caller and must outlive this instance.
   void set_delegate(Delegate* delegate) { delegate_ = delegate; }
 
@@ skipping 11 matching lines @@
   // Owned by the caller.
   Delegate* delegate_ = nullptr;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ArcBridgeBootstrap);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_ARC_BRIDGE_BOOTSTRAP_H_