sync: Plumb per-type counter observers to UI

Implements the plumbing to get events from the
DirectoryTypeDebugInfoEmitters in the ModelTypeRegistry, through the
SyncManager, SyncBackendHostCore, and SyncBackendHost to the
ProfileSyncService.

At the moment, there are no observers register and no events
are emitted.  Future patches will include logic to update the
counters and to expose their values on the about:sync page.

BUG=328606

Review URL: https://codereview.chromium.org/269543020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@268747 0039d316-1c4b-4281-b951-d872f2087c98

22 files changed, 378 insertions, 2 deletions

diff --git a/chrome/browser/sync/glue/sync_backend_host.h b/chrome/browser/sync/glue/sync_backend_host.h
index e9fb105..96d9176 100644
--- a/chrome/browser/sync/glue/sync_backend_host.h
+++ b/chrome/browser/sync/glue/sync_backend_host.h
@@ -215,6 +215,14 @@ class SyncBackendHost : public BackendDataTypeConfigurer {
       base::Callback<void(const std::vector<syncer::ModelType>&,
                           ScopedVector<base::ListValue>)> type) = 0;
 
+  // Enables the sending of directory type debug counters.  Also, for every
+  // time it is called, it makes an explicit request that updates to an update
+  // for all counters be emitted.
+  virtual void EnableDirectoryTypeDebugInfoForwarding() = 0;
+
+  // Disables the sending of directory type debug counters.
+  virtual void DisableDirectoryTypeDebugInfoForwarding() = 0;
+
   virtual base::MessageLoop* GetSyncLoopForTesting() = 0;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHost);
diff --git a/chrome/browser/sync/glue/sync_backend_host_core.cc b/chrome/browser/sync/glue/sync_backend_host_core.cc
index b5e2eb3..32b7da2 100644
--- a/chrome/browser/sync/glue/sync_backend_host_core.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_core.cc
@@ -15,7 +15,10 @@
 #include "sync/internal_api/public/events/protocol_event.h"
 #include "sync/internal_api/public/http_post_provider_factory.h"
 #include "sync/internal_api/public/internal_components_factory.h"
+#include "sync/internal_api/public/sessions/commit_counters.h"
+#include "sync/internal_api/public/sessions/status_counters.h"
 #include "sync/internal_api/public/sessions/sync_session_snapshot.h"
+#include "sync/internal_api/public/sessions/update_counters.h"
 #include "sync/internal_api/public/sync_core_proxy.h"
 #include "sync/internal_api/public/sync_manager.h"
 #include "sync/internal_api/public/sync_manager_factory.h"
@@ -300,6 +303,33 @@ void SyncBackendHostCore::OnPassphraseTypeChanged(
       type, passphrase_time);
 }
 
+void SyncBackendHostCore::OnCommitCountersUpdated(
+    syncer::ModelType type,
+    const syncer::CommitCounters& counters) {
+  host_.Call(
+      FROM_HERE,
+      &SyncBackendHostImpl::HandleDirectoryCommitCountersUpdatedOnFrontendLoop,
+      type, counters);
+}
+
+void SyncBackendHostCore::OnUpdateCountersUpdated(
+    syncer::ModelType type,
+    const syncer::UpdateCounters& counters) {
+  host_.Call(
+      FROM_HERE,
+      &SyncBackendHostImpl::HandleDirectoryUpdateCountersUpdatedOnFrontendLoop,
+      type, counters);
+}
+
+void SyncBackendHostCore::OnStatusCountersUpdated(
+    syncer::ModelType type,
+    const syncer::StatusCounters& counters) {
+  host_.Call(
+      FROM_HERE,
+      &SyncBackendHostImpl::HandleDirectoryStatusCountersUpdatedOnFrontendLoop,
+      type, counters);
+}
+
 void SyncBackendHostCore::OnActionableError(
     const syncer::SyncProtocolError& sync_error) {
   if (!sync_loop_)
@@ -548,6 +578,7 @@ void SyncBackendHostCore::DoDestroySyncManager() {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   if (sync_manager_) {
     save_changes_timer_.reset();
+    DisableDirectoryTypeDebugInfoForwarding();
     sync_manager_->RemoveObserver(this);
     sync_manager_->ShutdownOnSyncThread();
     sync_manager_.reset();
@@ -636,6 +667,19 @@ void SyncBackendHostCore::DisableProtocolEventForwarding() {
   forward_protocol_events_ = false;
 }
 
+void SyncBackendHostCore::EnableDirectoryTypeDebugInfoForwarding() {
+  DCHECK(sync_manager_);
+  if (!sync_manager_->HasDirectoryTypeDebugInfoObserver(this))
+    sync_manager_->RegisterDirectoryTypeDebugInfoObserver(this);
+  sync_manager_->RequestEmitDebugInfo();
+}
+
+void SyncBackendHostCore::DisableDirectoryTypeDebugInfoForwarding() {
+  DCHECK(sync_manager_);
+  if (sync_manager_->HasDirectoryTypeDebugInfoObserver(this))
+    sync_manager_->UnregisterDirectoryTypeDebugInfoObserver(this);
+}
+
 void SyncBackendHostCore::DeleteSyncDataFolder() {
   DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
   if (base::DirectoryExists(sync_data_folder_path_)) {
diff --git a/chrome/browser/sync/glue/sync_backend_host_core.h b/chrome/browser/sync/glue/sync_backend_host_core.h
index eb267a6..4ae89c7 100644
--- a/chrome/browser/sync/glue/sync_backend_host_core.h
+++ b/chrome/browser/sync/glue/sync_backend_host_core.h
@@ -11,6 +11,7 @@
 #include "chrome/browser/sync/glue/sync_backend_host_impl.h"
 #include "components/sync_driver/system_encryptor.h"
 #include "sync/internal_api/public/base/cancelation_signal.h"
+#include "sync/internal_api/public/sessions/type_debug_info_observer.h"
 #include "sync/internal_api/public/sync_encryption_handler.h"
 #include "url/gurl.h"
 
@@ -79,7 +80,8 @@ struct DoConfigureSyncerTypes {
 class SyncBackendHostCore
     : public base::RefCountedThreadSafe<SyncBackendHostCore>,
       public syncer::SyncEncryptionHandler::Observer,
-      public syncer::SyncManager::Observer {
+      public syncer::SyncManager::Observer,
+      public syncer::TypeDebugInfoObserver {
  public:
   SyncBackendHostCore(const std::string& name,
        const base::FilePath& sync_data_folder_path,
@@ -121,6 +123,17 @@ class SyncBackendHostCore
   virtual void OnPassphraseTypeChanged(syncer::PassphraseType type,
                                        base::Time passphrase_time) OVERRIDE;
 
+  // TypeDebugInfoObserver implementation
+  virtual void OnCommitCountersUpdated(
+      syncer::ModelType type,
+      const syncer::CommitCounters& counters) OVERRIDE;
+  virtual void OnUpdateCountersUpdated(
+      syncer::ModelType type,
+      const syncer::UpdateCounters& counters) OVERRIDE;
+  virtual void OnStatusCountersUpdated(
+      syncer::ModelType type,
+      const syncer::StatusCounters& counters) OVERRIDE;
+
   // Forwards an invalidation state change to the sync manager.
   void DoOnInvalidatorStateChange(syncer::InvalidatorState state);
 
@@ -212,6 +225,14 @@ class SyncBackendHostCore
   void SendBufferedProtocolEventsAndEnableForwarding();
   void DisableProtocolEventForwarding();
 
+  // Enables the forwarding of directory type debug counters to the
+  // SyncBackendHost.  Also requests that updates to all counters be
+  // emitted right away to initialize any new listeners' states.
+  void EnableDirectoryTypeDebugInfoForwarding();
+
+  // Disables forwarding of directory type debug counters.
+  void DisableDirectoryTypeDebugInfoForwarding();
+
   // Delete the sync data folder to cleanup backend data.  Happens the first
   // time sync is enabled for a user (to prevent accidentally reusing old
   // sync databases), as well as shutdown when you're no longer syncing.
diff --git a/chrome/browser/sync/glue/sync_backend_host_impl.cc b/chrome/browser/sync/glue/sync_backend_host_impl.cc
index ac4eacd..cee5863 100644
--- a/chrome/browser/sync/glue/sync_backend_host_impl.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_impl.cc
@@ -500,6 +500,24 @@ void SyncBackendHostImpl::DisableProtocolEventForwarding() {
           core_));
 }
 
+void SyncBackendHostImpl::EnableDirectoryTypeDebugInfoForwarding() {
+  DCHECK(initialized());
+  registrar_->sync_thread()->message_loop()->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &SyncBackendHostCore::EnableDirectoryTypeDebugInfoForwarding,
+          core_));
+}
+
+void SyncBackendHostImpl::DisableDirectoryTypeDebugInfoForwarding() {
+  DCHECK(initialized());
+  registrar_->sync_thread()->message_loop()->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &SyncBackendHostCore::DisableDirectoryTypeDebugInfoForwarding,
+          core_));
+}
+
 void SyncBackendHostImpl::GetAllNodesForTypes(
     syncer::ModelTypeSet types,
     base::Callback<void(const std::vector<syncer::ModelType>&,
@@ -796,6 +814,30 @@ void SyncBackendHostImpl::HandleProtocolEventOnFrontendLoop(
   frontend_->OnProtocolEvent(*scoped_event);
 }
 
+void SyncBackendHostImpl::HandleDirectoryCommitCountersUpdatedOnFrontendLoop(
+    syncer::ModelType type,
+    const syncer::CommitCounters& counters) {
+  if (!frontend_)
+    return;
+  frontend_->OnDirectoryTypeCommitCounterUpdated(type, counters);
+}
+
+void SyncBackendHostImpl::HandleDirectoryUpdateCountersUpdatedOnFrontendLoop(
+    syncer::ModelType type,
+    const syncer::UpdateCounters& counters) {
+  if (!frontend_)
+    return;
+  frontend_->OnDirectoryTypeUpdateCounterUpdated(type, counters);
+}
+
+void SyncBackendHostImpl::HandleDirectoryStatusCountersUpdatedOnFrontendLoop(
+    syncer::ModelType type,
+    const syncer::StatusCounters& counters) {
+  if (!frontend_)
+    return;
+  frontend_->OnDirectoryTypeStatusCounterUpdated(type, counters);
+}
+
 base::MessageLoop* SyncBackendHostImpl::GetSyncLoopForTesting() {
   return registrar_->sync_thread()->message_loop();
 }
diff --git a/chrome/browser/sync/glue/sync_backend_host_impl.h b/chrome/browser/sync/glue/sync_backend_host_impl.h
index 9ba56b3..1a156dc 100644
--- a/chrome/browser/sync/glue/sync_backend_host_impl.h
+++ b/chrome/browser/sync/glue/sync_backend_host_impl.h
@@ -21,6 +21,7 @@
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/internal_api/public/configure_reason.h"
 #include "sync/internal_api/public/sessions/sync_session_snapshot.h"
+#include "sync/internal_api/public/sessions/type_debug_info_observer.h"
 #include "sync/internal_api/public/sync_manager.h"
 #include "sync/internal_api/public/util/report_unrecoverable_error_function.h"
 #include "sync/internal_api/public/util/unrecoverable_error_handler.h"
@@ -127,6 +128,8 @@ class SyncBackendHostImpl
   virtual SyncedDeviceTracker* GetSyncedDeviceTracker() const OVERRIDE;
   virtual void RequestBufferedProtocolEventsAndEnableForwarding() OVERRIDE;
   virtual void DisableProtocolEventForwarding() OVERRIDE;
+  virtual void EnableDirectoryTypeDebugInfoForwarding() OVERRIDE;
+  virtual void DisableDirectoryTypeDebugInfoForwarding() OVERRIDE;
   virtual void GetAllNodesForTypes(
       syncer::ModelTypeSet types,
       base::Callback<void(const std::vector<syncer::ModelType>&,
@@ -183,6 +186,27 @@ class SyncBackendHostImpl
   // forwarding these events.
   void HandleProtocolEventOnFrontendLoop(syncer::ProtocolEvent* event);
 
+  // Forwards a directory commit counter update to the frontend loop.  Will not
+  // be called unless a call to EnableDirectoryTypeDebugInfoForwarding()
+  // explicitly requested that we start forwarding these events.
+  void HandleDirectoryCommitCountersUpdatedOnFrontendLoop(
+      syncer::ModelType type,
+      const syncer::CommitCounters& counters);
+
+  // Forwards a directory update counter update to the frontend loop.  Will not
+  // be called unless a call to EnableDirectoryTypeDebugInfoForwarding()
+  // explicitly requested that we start forwarding these events.
+  void HandleDirectoryUpdateCountersUpdatedOnFrontendLoop(
+      syncer::ModelType type,
+      const syncer::UpdateCounters& counters);
+
+  // Forwards a directory status counter update to the frontend loop.  Will not
+  // be called unless a call to EnableDirectoryTypeDebugInfoForwarding()
+  // explicitly requested that we start forwarding these events.
+  void HandleDirectoryStatusCountersUpdatedOnFrontendLoop(
+      syncer::ModelType type,
+      const syncer::StatusCounters& counters);
+
   SyncFrontend* frontend() { return frontend_; }
 
  private:
diff --git a/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc b/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
index 239c38b..1d2ce7d 100644
--- a/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_impl_unittest.cc
@@ -32,6 +32,9 @@
 #include "sync/internal_api/public/engine/model_safe_worker.h"
 #include "sync/internal_api/public/http_bridge_network_resources.h"
 #include "sync/internal_api/public/network_resources.h"
+#include "sync/internal_api/public/sessions/commit_counters.h"
+#include "sync/internal_api/public/sessions/status_counters.h"
+#include "sync/internal_api/public/sessions/update_counters.h"
 #include "sync/internal_api/public/sync_manager_factory.h"
 #include "sync/internal_api/public/test/fake_sync_manager.h"
 #include "sync/internal_api/public/util/experiments.h"
@@ -87,6 +90,12 @@ class MockSyncFrontend : public SyncFrontend {
   MOCK_METHOD0(OnEncryptionComplete, void());
   MOCK_METHOD1(OnMigrationNeededForTypes, void(syncer::ModelTypeSet));
   MOCK_METHOD1(OnProtocolEvent, void(const syncer::ProtocolEvent&));
+  MOCK_METHOD2(OnDirectoryTypeCommitCounterUpdated,
+               void(syncer::ModelType, const syncer::CommitCounters&));
+  MOCK_METHOD2(OnDirectoryTypeUpdateCounterUpdated,
+               void(syncer::ModelType, const syncer::UpdateCounters&));
+  MOCK_METHOD2(OnDirectoryTypeStatusCounterUpdated,
+               void(syncer::ModelType, const syncer::StatusCounters&));
   MOCK_METHOD1(OnExperimentsChanged,
       void(const syncer::Experiments&));
   MOCK_METHOD1(OnActionableError,
diff --git a/chrome/browser/sync/glue/sync_backend_host_mock.cc b/chrome/browser/sync/glue/sync_backend_host_mock.cc
index aee76c6..b1257a0 100644
--- a/chrome/browser/sync/glue/sync_backend_host_mock.cc
+++ b/chrome/browser/sync/glue/sync_backend_host_mock.cc
@@ -118,6 +118,10 @@ void SyncBackendHostMock::RequestBufferedProtocolEventsAndEnableForwarding() {}
 
 void SyncBackendHostMock::DisableProtocolEventForwarding() {}
 
+void SyncBackendHostMock::EnableDirectoryTypeDebugInfoForwarding() {}
+
+void SyncBackendHostMock::DisableDirectoryTypeDebugInfoForwarding() {}
+
 void SyncBackendHostMock::GetAllNodesForTypes(
     syncer::ModelTypeSet types,
     base::Callback<void(const std::vector<syncer::ModelType>& type,
diff --git a/chrome/browser/sync/glue/sync_backend_host_mock.h b/chrome/browser/sync/glue/sync_backend_host_mock.h
index 0b0782d..42cfeae 100644
--- a/chrome/browser/sync/glue/sync_backend_host_mock.h
+++ b/chrome/browser/sync/glue/sync_backend_host_mock.h
@@ -98,6 +98,9 @@ class SyncBackendHostMock : public SyncBackendHost {
   virtual void RequestBufferedProtocolEventsAndEnableForwarding() OVERRIDE;
   virtual void DisableProtocolEventForwarding() OVERRIDE;
 
+  virtual void EnableDirectoryTypeDebugInfoForwarding() OVERRIDE;
+  virtual void DisableDirectoryTypeDebugInfoForwarding() OVERRIDE;
+
   virtual void GetAllNodesForTypes(
       syncer::ModelTypeSet types,
       base::Callback<void(const std::vector<syncer::ModelType>& type,
diff --git a/chrome/browser/sync/profile_sync_service.cc b/chrome/browser/sync/profile_sync_service.cc
index 7df9aa7..dd3caaf 100644
--- a/chrome/browser/sync/profile_sync_service.cc
+++ b/chrome/browser/sync/profile_sync_service.cc
@@ -77,6 +77,7 @@
 #include "sync/internal_api/public/configure_reason.h"
 #include "sync/internal_api/public/http_bridge_network_resources.h"
 #include "sync/internal_api/public/network_resources.h"
+#include "sync/internal_api/public/sessions/type_debug_info_observer.h"
 #include "sync/internal_api/public/sync_core_proxy.h"
 #include "sync/internal_api/public/sync_encryption_handler.h"
 #include "sync/internal_api/public/util/experiments.h"
@@ -554,6 +555,30 @@ void ProfileSyncService::OnProtocolEvent(
                     OnProtocolEvent(event));
 }
 
+void ProfileSyncService::OnDirectoryTypeCommitCounterUpdated(
+    syncer::ModelType type,
+    const syncer::CommitCounters& counters) {
+  FOR_EACH_OBSERVER(syncer::TypeDebugInfoObserver,
+                    type_debug_info_observers_,
+                    OnCommitCountersUpdated(type, counters));
+}
+
+void ProfileSyncService::OnDirectoryTypeUpdateCounterUpdated(
+    syncer::ModelType type,
+    const syncer::UpdateCounters& counters) {
+  FOR_EACH_OBSERVER(syncer::TypeDebugInfoObserver,
+                    type_debug_info_observers_,
+                    OnUpdateCountersUpdated(type, counters));
+}
+
+void ProfileSyncService::OnDirectoryTypeStatusCounterUpdated(
+    syncer::ModelType type,
+    const syncer::StatusCounters& counters) {
+  FOR_EACH_OBSERVER(syncer::TypeDebugInfoObserver,
+                    type_debug_info_observers_,
+                    OnStatusCountersUpdated(type, counters));
+}
+
 void ProfileSyncService::OnDataTypeRequestsSyncStartup(
     syncer::ModelType type) {
   DCHECK(syncer::UserTypes().Has(type));
@@ -935,6 +960,10 @@ void ProfileSyncService::OnBackendInitialized(
   non_blocking_data_type_manager_.ConnectSyncBackend(
       backend_->GetSyncCoreProxy());
 
+  if (type_debug_info_observers_.might_have_observers()) {
+    backend_->EnableDirectoryTypeDebugInfoForwarding();
+  }
+
   // If we have a cached passphrase use it to decrypt/encrypt data now that the
   // backend is initialized. We want to call this before notifying observers in
   // case this operation affects the "passphrase required" status.
@@ -2106,6 +2135,22 @@ void ProfileSyncService::RemoveProtocolEventObserver(
   }
 }
 
+void ProfileSyncService::AddTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* type_debug_info_observer) {
+  type_debug_info_observers_.AddObserver(type_debug_info_observer);
+  if (type_debug_info_observers_.might_have_observers() && backend_) {
+    backend_->EnableDirectoryTypeDebugInfoForwarding();
+  }
+}
+
+void ProfileSyncService::RemoveTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* type_debug_info_observer) {
+  type_debug_info_observers_.RemoveObserver(type_debug_info_observer);
+  if (!type_debug_info_observers_.might_have_observers() && backend_) {
+    backend_->DisableDirectoryTypeDebugInfoForwarding();
+  }
+}
+
 namespace {
 
 class GetAllNodesRequestHelper
diff --git a/chrome/browser/sync/profile_sync_service.h b/chrome/browser/sync/profile_sync_service.h
index 78b510d..bb600b6 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -72,7 +72,10 @@ class SyncSessionSnapshot;
 namespace syncer {
 class BaseTransaction;
 class NetworkResources;
+struct CommitCounters;
+struct StatusCounters;
 struct SyncCredentials;
+struct UpdateCounters;
 struct UserShare;
 }  // namespace syncer
 
@@ -276,6 +279,9 @@ class ProfileSyncService : public ProfileSyncServiceBase,
   void RemoveProtocolEventObserver(
       browser_sync::ProtocolEventObserver* observer);
 
+  void AddTypeDebugInfoObserver(syncer::TypeDebugInfoObserver* observer);
+  void RemoveTypeDebugInfoObserver(syncer::TypeDebugInfoObserver* observer);
+
   // Asynchronously fetches base::Value representations of all sync nodes and
   // returns them to the specified callback on this thread.
   //
@@ -385,6 +391,15 @@ class ProfileSyncService : public ProfileSyncServiceBase,
       bool success) OVERRIDE;
   virtual void OnSyncCycleCompleted() OVERRIDE;
   virtual void OnProtocolEvent(const syncer::ProtocolEvent& event) OVERRIDE;
+  virtual void OnDirectoryTypeCommitCounterUpdated(
+      syncer::ModelType type,
+      const syncer::CommitCounters& counters) OVERRIDE;
+  virtual void OnDirectoryTypeUpdateCounterUpdated(
+      syncer::ModelType type,
+      const syncer::UpdateCounters& counters) OVERRIDE;
+  virtual void OnDirectoryTypeStatusCounterUpdated(
+      syncer::ModelType type,
+      const syncer::StatusCounters& counters) OVERRIDE;
   virtual void OnSyncConfigureRetry() OVERRIDE;
   virtual void OnConnectionStatusChange(
       syncer::ConnectionStatus status) OVERRIDE;
@@ -950,6 +965,7 @@ class ProfileSyncService : public ProfileSyncServiceBase,
 
   ObserverList<ProfileSyncServiceBase::Observer> observers_;
   ObserverList<browser_sync::ProtocolEventObserver> protocol_event_observers_;
+  ObserverList<syncer::TypeDebugInfoObserver> type_debug_info_observers_;
 
   syncer::SyncJsController sync_js_controller_;
 
diff --git a/components/sync_driver/sync_frontend.h b/components/sync_driver/sync_frontend.h
index 47d76be..0a360a8 100644
--- a/components/sync_driver/sync_frontend.h
+++ b/components/sync_driver/sync_frontend.h
@@ -16,6 +16,9 @@ namespace syncer {
 class DataTypeDebugInfoListener;
 class JsBackend;
 class ProtocolEvent;
+struct CommitCounters;
+struct StatusCounters;
+struct UpdateCounters;
 }  // namespace syncer
 
 namespace sync_pb {
@@ -62,6 +65,30 @@ class SyncFrontend {
   // is listening for it.
   virtual void OnProtocolEvent(const syncer::ProtocolEvent& event) = 0;
 
+  // Called when we receive an updated commit counter for a directory type.
+  //
+  // Disabled by default.  Enable by calling
+  // EnableDirectoryTypeDebugInfoForwarding() on the backend.
+  virtual void OnDirectoryTypeCommitCounterUpdated(
+      syncer::ModelType type,
+      const syncer::CommitCounters& counters) = 0;
+
+  // Called when we receive an updated update counter for a directory type.
+  //
+  // Disabled by default.  Enable by calling
+  // EnableDirectoryTypeDebugInfoForwarding() on the backend.
+  virtual void OnDirectoryTypeUpdateCounterUpdated(
+      syncer::ModelType type,
+      const syncer::UpdateCounters& counters) = 0;
+
+  // Called when we receive an updated status counter for a directory type.
+  //
+  // Disabled by default.  Enable by calling
+  // EnableDirectoryTypeDebugInfoForwarding() on the backend.
+  virtual void OnDirectoryTypeStatusCounterUpdated(
+      syncer::ModelType type,
+      const syncer::StatusCounters& counters) = 0;
+
   // The status of the connection to the sync server has changed.
   virtual void OnConnectionStatusChange(
       syncer::ConnectionStatus status) = 0;
diff --git a/sync/internal_api/public/sync_manager.h b/sync/internal_api/public/sync_manager.h
index 7488586..5b5f337 100644
--- a/sync/internal_api/public/sync_manager.h
+++ b/sync/internal_api/public/sync_manager.h
@@ -45,10 +45,11 @@ class HttpPostProviderFactory;
 class InternalComponentsFactory;
 class JsBackend;
 class JsEventHandler;
+class ProtocolEvent;
 class SyncCoreProxy;
 class SyncEncryptionHandler;
-class ProtocolEvent;
 class SyncScheduler;
+class TypeDebugInfoObserver;
 struct Experiments;
 struct UserShare;
 
@@ -361,6 +362,18 @@ class SYNC_EXPORT SyncManager : public syncer::InvalidationHandler {
 
   // Returns any buffered protocol events.  Does not clear the buffer.
   virtual ScopedVector<syncer::ProtocolEvent> GetBufferedProtocolEvents() = 0;
+
+  // Functions to manage registrations of DebugInfoObservers.
+  virtual void RegisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) = 0;
+  virtual void UnregisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) = 0;
+  virtual bool HasDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) = 0;
+
+  // Request that all current counter values be emitted as though they had just
+  // been updated.  Useful for initializing new observers' state.
+  virtual void RequestEmitDebugInfo() = 0;
 };
 
 }  // namespace syncer
diff --git a/sync/internal_api/public/test/fake_sync_manager.h b/sync/internal_api/public/test/fake_sync_manager.h
index 55e4f3b..9b08831 100644
--- a/sync/internal_api/public/test/fake_sync_manager.h
+++ b/sync/internal_api/public/test/fake_sync_manager.h
@@ -130,6 +130,13 @@ class FakeSyncManager : public SyncManager {
   virtual scoped_ptr<base::ListValue> GetAllNodesForType(
       syncer::ModelType type) OVERRIDE;
   virtual void RefreshTypes(ModelTypeSet types) OVERRIDE;
+  virtual void RegisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual void UnregisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual bool HasDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual void RequestEmitDebugInfo() OVERRIDE;
 
  private:
   scoped_refptr<base::SequencedTaskRunner> sync_task_runner_;
diff --git a/sync/internal_api/sync_backup_manager.cc b/sync/internal_api/sync_backup_manager.cc
index f255ae6..10215be 100644
--- a/sync/internal_api/sync_backup_manager.cc
+++ b/sync/internal_api/sync_backup_manager.cc
@@ -109,4 +109,15 @@ void SyncBackupManager::NormalizeEntries() {
   unsynced_.clear();
 }
 
+void SyncBackupManager::RegisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {}
+
+void SyncBackupManager::UnregisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {}
+
+bool SyncBackupManager::HasDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) { return false; }
+
+void SyncBackupManager::RequestEmitDebugInfo() {}
+
 }  // namespace syncer
diff --git a/sync/internal_api/sync_backup_manager.h b/sync/internal_api/sync_backup_manager.h
index 1bee105..e6b9ca4 100644
--- a/sync/internal_api/sync_backup_manager.h
+++ b/sync/internal_api/sync_backup_manager.h
@@ -48,6 +48,14 @@ class SYNC_EXPORT_PRIVATE SyncBackupManager : public SyncRollbackManagerBase {
       const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
       syncable::BaseTransaction* trans) OVERRIDE;
 
+  virtual void RegisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual void UnregisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual bool HasDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual void RequestEmitDebugInfo() OVERRIDE;
+
  private:
   // Replaces local IDs with server IDs and clear unsynced bit of modified
   // entries.
diff --git a/sync/internal_api/sync_manager_impl.cc b/sync/internal_api/sync_manager_impl.cc
index 60bd3da..c2894b4 100644
--- a/sync/internal_api/sync_manager_impl.cc
+++ b/sync/internal_api/sync_manager_impl.cc
@@ -1126,6 +1126,25 @@ ScopedVector<syncer::ProtocolEvent>
   return protocol_event_buffer_.GetBufferedProtocolEvents();
 }
 
+void SyncManagerImpl::RegisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {
+  model_type_registry_->RegisterDirectoryTypeDebugInfoObserver(observer);
+}
+
+void SyncManagerImpl::UnregisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {
+  model_type_registry_->UnregisterDirectoryTypeDebugInfoObserver(observer);
+}
+
+bool SyncManagerImpl::HasDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {
+  return model_type_registry_->HasDirectoryTypeDebugInfoObserver(observer);
+}
+
+void SyncManagerImpl::RequestEmitDebugInfo() {
+  model_type_registry_->RequestEmitDebugInfo();
+}
+
 // static.
 int SyncManagerImpl::GetDefaultNudgeDelay() {
   return kDefaultNudgeDelayMilliseconds;
diff --git a/sync/internal_api/sync_manager_impl.h b/sync/internal_api/sync_manager_impl.h
index 653e48a..9402737 100644
--- a/sync/internal_api/sync_manager_impl.h
+++ b/sync/internal_api/sync_manager_impl.h
@@ -35,6 +35,7 @@ namespace syncer {
 class ModelTypeRegistry;
 class SyncAPIServerConnectionManager;
 class SyncCore;
+class TypeDebugInfoObserver;
 class WriteNode;
 class WriteTransaction;
 
@@ -121,6 +122,13 @@ class SYNC_EXPORT_PRIVATE SyncManagerImpl :
       GetBufferedProtocolEvents() OVERRIDE;
   virtual scoped_ptr<base::ListValue> GetAllNodesForType(
       syncer::ModelType type) OVERRIDE;
+  virtual void RegisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual void UnregisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual bool HasDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual void RequestEmitDebugInfo() OVERRIDE;
 
   // SyncEncryptionHandler::Observer implementation.
   virtual void OnPassphraseRequired(
diff --git a/sync/internal_api/sync_rollback_manager_base.cc b/sync/internal_api/sync_rollback_manager_base.cc
index 98fcd48..7d425cc 100644
--- a/sync/internal_api/sync_rollback_manager_base.cc
+++ b/sync/internal_api/sync_rollback_manager_base.cc
@@ -319,4 +319,15 @@ void SyncRollbackManagerBase::InitBookmarkFolder(const std::string& folder) {
   entry.PutSpecifics(specifics);
 }
 
+void SyncRollbackManagerBase::RegisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {}
+
+void SyncRollbackManagerBase::UnregisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {}
+
+bool SyncRollbackManagerBase::HasDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) { return false; }
+
+void SyncRollbackManagerBase::RequestEmitDebugInfo() {}
+
 }  // namespace syncer
diff --git a/sync/internal_api/sync_rollback_manager_base.h b/sync/internal_api/sync_rollback_manager_base.h
index d6ba564..ee8d4a3 100644
--- a/sync/internal_api/sync_rollback_manager_base.h
+++ b/sync/internal_api/sync_rollback_manager_base.h
@@ -113,6 +113,14 @@ class SYNC_EXPORT_PRIVATE SyncRollbackManagerBase :
       const syncable::ImmutableWriteTransactionInfo& write_transaction_info,
       ModelTypeSet models_with_changes) OVERRIDE;
 
+  virtual void RegisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual void UnregisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual bool HasDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer) OVERRIDE;
+  virtual void RequestEmitDebugInfo() OVERRIDE;
+
  private:
   void NotifyInitializationSuccess();
   void NotifyInitializationFailure();
diff --git a/sync/internal_api/test/fake_sync_manager.cc b/sync/internal_api/test/fake_sync_manager.cc
index c7873a8..5b0f121 100644
--- a/sync/internal_api/test/fake_sync_manager.cc
+++ b/sync/internal_api/test/fake_sync_manager.cc
@@ -253,6 +253,19 @@ void FakeSyncManager::RefreshTypes(ModelTypeSet types) {
   last_refresh_request_types_ = types;
 }
 
+void FakeSyncManager::RegisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {}
+
+void FakeSyncManager::UnregisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {}
+
+bool FakeSyncManager::HasDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {
+  return false;
+}
+
+void FakeSyncManager::RequestEmitDebugInfo() {}
+
 void FakeSyncManager::OnIncomingInvalidation(
       const ObjectIdInvalidationMap& invalidation_map) {
   // Do nothing.
diff --git a/sync/sessions/model_type_registry.cc b/sync/sessions/model_type_registry.cc
index 2b9e7cb..668f8da 100644
--- a/sync/sessions/model_type_registry.cc
+++ b/sync/sessions/model_type_registry.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop_proxy.h"
+#include "base/observer_list.h"
 #include "sync/engine/directory_commit_contributor.h"
 #include "sync/engine/directory_update_handler.h"
 #include "sync/engine/non_blocking_type_processor_core.h"
@@ -164,6 +165,32 @@ ModelTypeRegistry::directory_type_debug_info_emitter_map() {
   return &directory_type_debug_info_emitter_map_;
 }
 
+void ModelTypeRegistry::RegisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {
+  if (!type_debug_info_observers_.HasObserver(observer))
+    type_debug_info_observers_.AddObserver(observer);
+}
+
+void ModelTypeRegistry::UnregisterDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {
+  type_debug_info_observers_.RemoveObserver(observer);
+}
+
+bool ModelTypeRegistry::HasDirectoryTypeDebugInfoObserver(
+    syncer::TypeDebugInfoObserver* observer) {
+  return type_debug_info_observers_.HasObserver(observer);
+}
+
+void ModelTypeRegistry::RequestEmitDebugInfo() {
+  for (DirectoryTypeDebugInfoEmitterMap::iterator it =
+       directory_type_debug_info_emitter_map_.begin();
+       it != directory_type_debug_info_emitter_map_.end(); ++it) {
+    it->second->EmitCommitCountersUpdate();
+    it->second->EmitUpdateCountersUpdate();
+    it->second->EmitStatusCountersUpdate();
+  }
+}
+
 ModelTypeSet ModelTypeRegistry::GetEnabledDirectoryTypes() const {
   return enabled_directory_types_;
 }
diff --git a/sync/sessions/model_type_registry.h b/sync/sessions/model_type_registry.h
index 3ee36c7..20d6d20 100644
--- a/sync/sessions/model_type_registry.h
+++ b/sync/sessions/model_type_registry.h
@@ -73,6 +73,14 @@ class SYNC_EXPORT_PRIVATE ModelTypeRegistry {
   CommitContributorMap* commit_contributor_map();
   DirectoryTypeDebugInfoEmitterMap* directory_type_debug_info_emitter_map();
 
+  void RegisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer);
+  void UnregisterDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer);
+  bool HasDirectoryTypeDebugInfoObserver(
+      syncer::TypeDebugInfoObserver* observer);
+  void RequestEmitDebugInfo();
+
  private:
   ModelTypeSet GetEnabledNonBlockingTypes() const;
   ModelTypeSet GetEnabledDirectoryTypes() const;