sync: make scheduling logic and job ownership more obvious.

sync/sessions/sync_session.h

Index: sync/sessions/sync_session.h
diff --git a/sync/sessions/sync_session.h b/sync/sessions/sync_session.h
index 93d7f4161c3f2e745c30bb219d2d3cd9dcff7bfd..4026e88aa9b602ba1f4e17899729ad7799d0691e 100644
--- a/sync/sessions/sync_session.h
+++ b/sync/sessions/sync_session.h
@@ -112,25 +112,11 @@ class SyncSession {
   // engine again.
   bool HasMoreToSync() const;
 
-  // Returns true if we completely ran the session without errors.
-  //
-  // There are many errors that could prevent a sync cycle from succeeding.
-  // These include invalid local state, inability to contact the server,
-  // inability to authenticate with the server, and server errors.  What they
-  // have in common is that the we either need to take some action and then
-  // retry the sync cycle or, in the case of transient errors, retry after some
-  // backoff timer has expired.  Most importantly, the SyncScheduler should not
-  // assume that the original action that triggered the sync cycle (ie. a nudge
-  // or a notification) has been properly serviced.
-  //
-  // This function also returns false if SyncShare has not been called on this
-  // session yet, or if ResetTransientState() has been called on this session
-  // since the last call to SyncShare.
-  bool Succeeded() const;
-
-  // Returns true if we reached the server successfully and the server did not
-  // return any error codes. Returns false if no connection was attempted.
-  bool SuccessfullyReachedServer() const;
+  // Returns true if we reached the server. Note that "reaching the server"
+  // here means that from an HTTP perspective, we succeeded (HTTP 200).  The
+  // server **MAY** have returned a sync protocol error.
+  // See SERVER_RETURN_* in the SyncerError enum for values.
+  bool DidReachServer() const;
 
   // Collects all state pertaining to how and why |s| originated and unions it
   // with corresponding state in |this|, leaving |s| unchanged.  Allows |this|
@@ -139,11 +125,13 @@ class SyncSession {
   // sessions.
   void Coalesce(const SyncSession& session);
 
-  // Compares the routing_info_, workers and payload map with the passed in
-  // session. Purges types from the above 3 which are not in session. Useful
+  // Compares the routing_info_, workers and payload map with those passed in.
+  // Purges types from the above 3 which are not present in latest. Useful
   // to update the sync session when the user has disabled some types from
   // syncing.
-  void RebaseRoutingInfoWithLatest(const SyncSession& session);
+  void RebaseRoutingInfoWithLatest(
+      const ModelSafeRoutingInfo& routing_info,
+      const std::vector<ModelSafeWorker*>& workers);
 
   // Should be called any time |this| is being re-used in a new call to
   // SyncShare (e.g., HasMoreToSync returned true).
@@ -177,9 +165,6 @@ class SyncSession {
   // Returns the set of enabled groups that have conflicts.
   std::set<ModelSafeGroup> GetEnabledGroupsWithConflicts() const;
 
-  // Mark the session has having finished all the sync steps it needed.
-  void SetFinished();
-
  private:
   // Extend the encapsulation boundary to utilities for internal member
   // assignments. This way, the scope of these actions is explicit, they can't
@@ -217,10 +202,6 @@ class SyncSession {
   // |routing_info_|.
   std::set<ModelSafeGroup> enabled_groups_;
 
-  // Whether this session has reached its last step or not. Gets reset on each
-  // new cycle (via PrepareForAnotherSyncCycle).
-  bool finished_;
-
   DISALLOW_COPY_AND_ASSIGN(SyncSession);
 };