[Sync] SyncEngine refactor part 1: interfaces.

components/sync/driver/glue/sync_backend_host_core.h

Index: components/sync/driver/glue/sync_backend_host_core.h
diff --git a/components/sync/driver/glue/sync_backend_host_core.h b/components/sync/driver/glue/sync_backend_host_core.h
index 81b60d9b9e96ba37ec54646be5eb496268c9308f..a9e8179e1d3a363462c01f8040eda86949a55232 100644
--- a/components/sync/driver/glue/sync_backend_host_core.h
+++ b/components/sync/driver/glue/sync_backend_host_core.h
@@ -83,7 +83,7 @@ struct DoInitializeOptions {
 };
 
 // Helper struct to handle currying params to
-// SyncBackendHost::Core::DoConfigureSyncer.
+// SyncBackendHostCore::DoConfigureSyncer.
 struct DoConfigureSyncerTypes {
   DoConfigureSyncerTypes();
   DoConfigureSyncerTypes(const DoConfigureSyncerTypes& other);
@@ -156,17 +156,16 @@ class SyncBackendHostCore
 
   // Note:
   //
-  // The Do* methods are the various entry points from our
-  // SyncBackendHost.  They are all called on the sync thread to
-  // actually perform synchronous (and potentially blocking) syncapi
-  // operations.
+  // The Do* methods are the various entry points from our SyncBackendHostImpl.
+  // They are all called on the sync thread to actually perform synchronous (and
+  // potentially blocking) syncapi operations.
   //
   // Called to perform initialization of the syncapi on behalf of
-  // SyncBackendHost::Initialize.
+  // SyncEngine::Initialize.
   void DoInitialize(std::unique_ptr<DoInitializeOptions> options);
 
   // Called to perform credential update on behalf of
-  // SyncBackendHost::UpdateCredentials.
+  // SyncEngine::UpdateCredentials.
   void DoUpdateCredentials(const SyncCredentials& credentials);
 
   // Called to tell the syncapi to start syncing (generally after
@@ -189,7 +188,7 @@ class SyncBackendHostCore
   void DoRefreshTypes(ModelTypeSet types);
 
   // Invoked if we failed to download the necessary control types at startup.
-  // Invokes SyncBackendHost::HandleControlTypesDownloadRetry.
+  // Invokes SyncEngine::HandleControlTypesDownloadRetry.
   void OnControlTypesDownloadRetry();
 
   // Called to perform tasks which require the control data to be downloaded.
@@ -226,9 +225,9 @@ 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.
+  // Enables the forwarding of directory type debug counters to the SyncEngine.

[skym, 2016/12/02 20:54:54]

But, this class, SyncBackxendHostCore, is part of what constitutes sync's
engine. Everything on the sync thread is part of our engine, right? This
interface name doesn't make sense for anything that's actually in the engine to
refer to. Maybe it'd be better we had left hand and right hand side interfaces
the SyncBackendHostImpl.

[maxbogue, 2016/12/02 23:59:27]

Fixed to SyncEngineHost (the thing listening to the sync engine).

And your last sentence is what this entire refactoring project is allll about :)

+  // 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.
@@ -275,7 +274,7 @@ class SyncBackendHostCore
   // Path of the folder that stores the sync data files.
   const base::FilePath sync_data_folder_path_;
 
-  // Our parent SyncBackendHost.
+  // Our parent SyncBackendHostImpl.
   WeakHandle<SyncBackendHostImpl> host_;
 
   // Our parent's registrar (not owned).  Non-null only between