[Sync] SyncEngine refactor part 1: interfaces.

components/sync/engine/sync_engine_host.h

 // 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 COMPONENTS_SYNC_DRIVER_SYNC_FRONTEND_H_
-#define COMPONENTS_SYNC_DRIVER_SYNC_FRONTEND_H_
+#ifndef COMPONENTS_SYNC_ENGINE_SYNC_ENGINE_HOST_H_
+#define COMPONENTS_SYNC_ENGINE_SYNC_ENGINE_HOST_H_
 
 #include <string>
 
 #include "components/sync/base/model_type.h"
 #include "components/sync/base/weak_handle.h"
 #include "components/sync/engine/sync_encryption_handler.h"
 #include "components/sync/engine/sync_manager.h"
 #include "components/sync/protocol/sync_protocol_error.h"
 
 namespace sync_pb {
 class EncryptedData;
 }  // namespace sync_pb
 
 namespace syncer {
 
 class DataTypeDebugInfoListener;
 class JsBackend;
 class ProtocolEvent;
 struct CommitCounters;
 struct StatusCounters;
 struct UpdateCounters;
 
-// SyncFrontend is the interface used by SyncBackendHost to communicate with
-// the entity that created it and, presumably, is interested in sync-related
-// activity.
-// NOTE: All methods will be invoked by a SyncBackendHost on the same thread
-// used to create that SyncBackendHost.
-class SyncFrontend {
+// SyncEngineHost is the interface used by SyncEngine to communicate with the
+// entity that created it. It's essentially an observer interface except the
+// SyncEngine always has exactly one.
+class SyncEngineHost {
  public:
-  SyncFrontend();
-  virtual ~SyncFrontend();
+  SyncEngineHost();
+  virtual ~SyncEngineHost();
 
   // The backend has completed initialization and it is now ready to
   // accept and process changes.  If success is false, initialization
   // wasn't able to be completed and should be retried.
   //
   // |js_backend| is what about:sync interacts with; it's different
   // from the 'Backend' in 'OnBackendInitialized' (unfortunately).  It
   // is initialized only if |success| is true.
   virtual void OnBackendInitialized(
       const WeakHandle<JsBackend>& js_backend,
       const WeakHandle<DataTypeDebugInfoListener>& debug_info_listener,
       const std::string& cache_guid,
       bool success) = 0;
 
   // The backend queried the server recently and received some updates.
   virtual void OnSyncCycleCompleted() = 0;
 
-  // Informs the frontned of some network event.  These notifications are
-  // disabled by default and must be enabled through an explicit request to the
-  // SyncBackendHost.
+  // Informs the host of some network event. These notifications are disabled by
+  // default and must be enabled through an explicit request to the SyncEngine.
   //
-  // It's disabld by default to avoid copying data across threads when no one
+  // It's disabled by default to avoid copying data across threads when no one
   // is listening for it.
   virtual void OnProtocolEvent(const 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(
       ModelType type,
       const CommitCounters& counters) = 0;
@@ skipping 14 matching lines @@
       ModelType type,
       const StatusCounters& counters) = 0;
 
   // The status of the connection to the sync server has changed.
   virtual void OnConnectionStatusChange(ConnectionStatus status) = 0;
 
   // The syncer requires a passphrase to decrypt sensitive updates. This is
   // called when the first sensitive data type is setup by the user and anytime
   // the passphrase is changed by another synced client. |reason| denotes why
   // the passphrase was required. |pending_keys| is a copy of the
-  // cryptographer's pending keys to be passed on to the frontend in order to
+  // cryptographer's pending keys to be passed on to the host in order to
   // be cached.
   virtual void OnPassphraseRequired(
       PassphraseRequiredReason reason,
       const sync_pb::EncryptedData& pending_keys) = 0;
 
   // Called when the passphrase provided by the user is
   // accepted. After this is called, updates to sensitive nodes are
   // encrypted using the accepted passphrase.
   virtual void OnPassphraseAccepted() = 0;
 
@@ skipping 12 matching lines @@
   virtual void OnEncryptedTypesChanged(ModelTypeSet encrypted_types,
                                        bool encrypt_everything) = 0;
 
   // Called after we finish encrypting the current set of encrypted
   // types.
   virtual void OnEncryptionComplete() = 0;
 
   // Called to perform migration of |types|.
   virtual void OnMigrationNeededForTypes(ModelTypeSet types) = 0;
 
-  // Inform the Frontend that new datatypes are available for registration.
+  // Called when new datatypes are available for registration.
   virtual void OnExperimentsChanged(const Experiments& experiments) = 0;
 
   // Called when the sync cycle returns there is an user actionable error.
   virtual void OnActionableError(const SyncProtocolError& error) = 0;
 
   // Called when the user of this device enables passphrase encryption.
   //
   // |nigori_state| contains the new (post custom passphrase) encryption keys
   // and can be used to restore SyncEncryptionHandler's state across sync
   // backend instances. See also SyncEncryptionHandlerImpl::RestoreNigori.
   virtual void OnLocalSetPassphraseEncryption(
       const SyncEncryptionHandler::NigoriState& nigori_state) = 0;
 };
 
 }  // namespace syncer
 
-#endif  // COMPONENTS_SYNC_DRIVER_SYNC_FRONTEND_H_
+#endif  // COMPONENTS_SYNC_ENGINE_SYNC_ENGINE_HOST_H_