[Sync] Notify the datatype of the current context on startup

In order to support context triggered refreshes, the datatype must know
what the current context is at startup to decide whether a refresh must
be performed or not. We will now invoke UpdateDataTypeContext before
MergeDataAndStartSyncing if a valid context exists.

BUG=357368
R=rlarocque@chromium.org

Review URL: https://codereview.chromium.org/233833003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@263376 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 17 insertions, 2 deletions

diff --git a/sync/internal_api/public/read_transaction.h b/sync/internal_api/public/read_transaction.h
index 02e2633..3a3dc8d 100644
--- a/sync/internal_api/public/read_transaction.h
+++ b/sync/internal_api/public/read_transaction.h
@@ -13,6 +13,10 @@ namespace tracked_objects {
 class Location;
 }  // namespace tracked_objects
 
+namespace sync_pb {
+class DataTypeContext;
+}
+
 namespace syncer {
 
 struct UserShare;
@@ -35,7 +39,11 @@ class SYNC_EXPORT ReadTransaction : public BaseTransaction {
 
   // Return |transaction_version| of |type| stored in sync directory's
   // persisted info.
-  int64 GetModelVersion(ModelType type);
+  int64 GetModelVersion(ModelType type) const;
+
+  // Fills |context| with the datatype context associated with |type|.
+  void GetDataTypeContext(ModelType type,
+                          sync_pb::DataTypeContext* context) const;
 
  private:
   void* operator new(size_t size);  // Transaction is meant for stack use only.
diff --git a/sync/internal_api/read_transaction.cc b/sync/internal_api/read_transaction.cc
index 81e5340..ebc56ec 100644
--- a/sync/internal_api/read_transaction.cc
+++ b/sync/internal_api/read_transaction.cc
@@ -36,8 +36,15 @@ syncable::BaseTransaction* ReadTransaction::GetWrappedTrans() const {
   return transaction_;
 }
 
-int64 ReadTransaction::GetModelVersion(ModelType type) {
+int64 ReadTransaction::GetModelVersion(ModelType type) const {
   return transaction_->directory()->GetTransactionVersion(type);
 }
 
+void ReadTransaction::GetDataTypeContext(
+    ModelType type,
+    sync_pb::DataTypeContext* context) const {
+  return transaction_->directory()->GetDataTypeContext(
+      transaction_, type, context);
+}
+
 }  // namespace syncer