arc: Revamp the ArcBridgeService interface

components/arc/metrics/arc_metrics_service.h

Index: components/arc/metrics/arc_metrics_service.h
diff --git a/components/arc/metrics/arc_metrics_service.h b/components/arc/metrics/arc_metrics_service.h
index 4f611787a280051268a6672f7880a0ccc4952347..7b7958be491de551ee11aff82606b3bd75450b3b 100644
--- a/components/arc/metrics/arc_metrics_service.h
+++ b/components/arc/metrics/arc_metrics_service.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef COMPONENTS_ARC_METRICS_ARC_METRICS_SERVICE_H
-#define COMPONENTS_ARC_METRICS_ARC_METRICS_SERVICE_H
+#ifndef COMPONENTS_ARC_METRICS_ARC_METRICS_SERVICE_H_
+#define COMPONENTS_ARC_METRICS_ARC_METRICS_SERVICE_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
@@ -12,24 +12,28 @@
 #include "components/arc/arc_bridge_service.h"
 #include "components/arc/arc_service.h"
 #include "components/arc/common/arc_bridge.mojom.h"
+#include "components/arc/instance_holder.h"
 #include "components/arc/metrics/oom_kills_monitor.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace arc {
 
 // Collects information from other ArcServices and send UMA metrics.
-class ArcMetricsService : public ArcService,
-                          public ArcBridgeService::Observer,
-                          public mojom::MetricsHost {
+class ArcMetricsService
+    : public ArcService,
+      public InstanceHolder<mojom::MetricsInstance>::Observer,
+      public mojom::MetricsHost {
  public:
   explicit ArcMetricsService(ArcBridgeService* bridge_service);
   ~ArcMetricsService() override;
 
-  // ArcBridgeService::Observer overrides.
-  void OnMetricsInstanceReady() override;
-  void OnMetricsInstanceClosed() override;
-  void OnProcessInstanceReady() override;
-  void OnProcessInstanceClosed() override;
+  // InstanceHolder<mojom::MetricsInstance>::Observer overrides.
+  void OnInstanceReady() override;
+  void OnInstanceClosed() override;
+
+  // Implementations for InstanceHolder<mojom::ProcessInstance>::Observer.
+  void OnProcessInstanceReady();
+  void OnProcessInstanceClosed();
 
   // MetricsHost overrides.
   void ReportBootProgress(
@@ -45,8 +49,24 @@ class ArcMetricsService : public ArcService,
   void OnArcStartTimeRetrieved(bool success, base::TimeTicks arc_start_time);
 
  private:
+  // Adapter to be able to also observe ProcessInstance events.
+  class ProcessObserver
+      : public InstanceHolder<mojom::ProcessInstance>::Observer {
+   public:
+    explicit ProcessObserver(ArcMetricsService* arc_metrics_service);
+    ~ProcessObserver() override;
+
+   private:
+    // InstanceHolder<mojom::ProcessInstance>::Observer overrides.
+    void OnInstanceReady() override;
+    void OnInstanceClosed() override;
+
+    ArcMetricsService* arc_metrics_service_;
+  };
+
   mojo::Binding<mojom::MetricsHost> binding_;
 
+  ProcessObserver process_observer_;
   base::ThreadChecker thread_checker_;
   base::RepeatingTimer timer_;
 
@@ -63,4 +83,4 @@ class ArcMetricsService : public ArcService,
 
 }  // namespace arc
 
-#endif  // COMPONENTS_ARC_METRICS_ARC_METRICS_SERVICE_H
+#endif  // COMPONENTS_ARC_METRICS_ARC_METRICS_SERVICE_H_