sync: Add pre-commit update avoidance mode + flag

sync/internal_api/public/internal_components_factory.h

 // Copyright 2012 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.
 //
 // InternalComponentsFactory exists so that tests can override creation of
 // components used by the SyncManager that are not exposed across the sync
 // API boundary.
 
 #ifndef SYNC_INTERNAL_API_PUBLIC_INTERNAL_COMPONENTS_FACTORY_H_
 #define SYNC_INTERNAL_API_PUBLIC_INTERNAL_COMPONENTS_FACTORY_H_
@@ skipping 32 matching lines @@
   };
 
   enum BackoffOverride {
     BACKOFF_NORMAL,
     // Use this value for integration testing to avoid long delays /
     // timing out tests. Uses kInitialBackoffShortRetrySeconds (see
     // polling_constants.h) for all initial retries.
     BACKOFF_SHORT_INITIAL_RETRY_OVERRIDE
   };
 
+  enum PreCommitUpdatesPolicy {
+    // By default, the server will enable or disable this experiment through the
+    // sync protocol's experiments data type.
+    SERVER_CONTROLLED_PRE_COMMIT_UPDATE_AVOIANCE,
+
+    // This flag overrides the server's decision and enables the pre-commit
+    // update avoidance experiment.
+    FORCE_ENABLE_PRE_COMMIT_UPDATE_AVOIDANCE,
+  };
+
   // Configuration options for internal components. This struct is expected
   // to grow and shrink over time with transient features / experiments,
   // roughly following command line flags in chrome. Implementations of
   // InternalComponentsFactory can use this information to build components
   // with appropriate bells and whistles.
   struct Switches {
     EncryptionMethod encryption_method;
     BackoffOverride backoff_override;
+    PreCommitUpdatesPolicy pre_commit_updates_policy;
   };
 
   virtual ~InternalComponentsFactory() {}
 
   virtual scoped_ptr<SyncScheduler> BuildScheduler(
       const std::string& name,
       sessions::SyncSessionContext* context) = 0;
 
   virtual scoped_ptr<sessions::SyncSessionContext> BuildContext(
       ServerConnectionManager* connection_manager,
@@ skipping 11 matching lines @@
       const base::FilePath& backing_filepath) = 0;
 
   // Returns the Switches struct that this object is using as configuration, if
   // the implementation is making use of one.
   virtual Switches GetSwitches() const = 0;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_INTERNAL_COMPONENTS_FACTORY_H_