[Sync] Add sync api support for context changes

The sync engine/api won't act on them yet; this just lays the groundwork for
passing context changes around.

BUG=345420

Review URL: https://codereview.chromium.org/220043002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@261469 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 13 insertions, 0 deletions

diff --git a/sync/api/sync_change_processor.cc b/sync/api/sync_change_processor.cc
index 4a0607e..f6c268c 100644
--- a/sync/api/sync_change_processor.cc
+++ b/sync/api/sync_change_processor.cc
@@ -10,4 +10,11 @@ SyncChangeProcessor::SyncChangeProcessor() {}
 
 SyncChangeProcessor::~SyncChangeProcessor() {}
 
+syncer::SyncError SyncChangeProcessor::UpdateDataTypeContext(
+    ModelType type,
+    const std::string& context) {
+  // Do nothing.
+  return syncer::SyncError();
+}
+
 }  // namespace syncer
diff --git a/sync/api/sync_change_processor.h b/sync/api/sync_change_processor.h
index 3cdf6a8..efc35f7 100644
--- a/sync/api/sync_change_processor.h
+++ b/sync/api/sync_change_processor.h
@@ -63,6 +63,12 @@ class SYNC_EXPORT SyncChangeProcessor {
   virtual void GetSyncData(const ModelType& type,
                            const std::string& sync_tag,
                            const GetSyncDataCallback& callback) const {}
+
+  // Updates the context for |type|. Default implementation does nothing.
+  // A type's context is a per-client blob that can affect all SyncData
+  // sent to/from the server, much like a cookie.
+  virtual syncer::SyncError UpdateDataTypeContext(ModelType type,
+                                                  const std::string& context);
 };
 
 }  // namespace syncer