sync: Introduce classes for per-type counters

sync/internal_api/public/sessions/type_debug_info_observer.h

Index: sync/internal_api/public/sessions/type_debug_info_observer.h
diff --git a/sync/internal_api/public/sessions/type_debug_info_observer.h b/sync/internal_api/public/sessions/type_debug_info_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..dc211c2d87b273680d6eff1bcb717244875adc79
--- /dev/null
+++ b/sync/internal_api/public/sessions/type_debug_info_observer.h
@@ -0,0 +1,35 @@
+// Copyright 2014 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 SYNC_INTERNAL_API_PUBLIC_SESSIONS_TYPE_DEBUG_INFO_OBSERVER_H_
+#define SYNC_INTERNAL_API_PUBLIC_SESSIONS_TYPE_DEBUG_INFO_OBSERVER_H_
+
+#include "sync/internal_api/public/base/model_type.h"
+
+namespace syncer {
+
+struct CommitCounters;
+struct StatusCounters;
+struct UpdateCounters;
+
+// Interface for classes that observe per-type sync debug counters.
+class SYNC_EXPORT TypeDebugInfoObserver {
+ public:
+  TypeDebugInfoObserver();
+  virtual ~TypeDebugInfoObserver();
+
+  virtual void OnCommitCountersUpdated(
+      syncer::ModelType type,
+      const CommitCounters& counters) = 0;
+  virtual void OnUpdateCountersUpdated(
+      syncer::ModelType type,
+      const UpdateCounters& counters) = 0;
+  virtual void OnStatusCountersUpdated(
+      syncer::ModelType type,
+      const StatusCounters& counters) = 0;
+};
+
+}  // namespace syncer
+
+#endif  // SYNC_INTERNAL_API_PUBLIC_SESSIONS_TYPE_DEBUG_INFO_OBSERVER_H_