sync: beginnings of MessageLoop based SyncerThread

chrome/browser/sync/sessions/sync_session.h

Index: chrome/browser/sync/sessions/sync_session.h
diff --git a/chrome/browser/sync/sessions/sync_session.h b/chrome/browser/sync/sessions/sync_session.h
index ce7c9e5dd11da04267ce648cf907b058190a2673..5226fb41267dd7262d0144a90801d3ab8598cadd 100644
--- a/chrome/browser/sync/sessions/sync_session.h
+++ b/chrome/browser/sync/sessions/sync_session.h
@@ -19,6 +19,7 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/ref_counted.h"
 #include "base/scoped_ptr.h"
 #include "base/time.h"
 #include "chrome/browser/sync/sessions/ordered_commit_set.h"
@@ -38,7 +39,7 @@ namespace sessions {
 typedef std::pair<sync_pb::GetUpdatesCallerInfo::GetUpdatesSource,
     syncable::ModelTypeBitSet> SyncSourceInfo;
 
-class SyncSession {
+class SyncSession : public base::RefCountedThreadSafe<SyncSession> {

[akalin, 2011/01/13 00:36:34]

Why does this have to be refcounted?

[tim (not reviewing), 2011/01/13 18:26:56]

I discussed this tradeoff in the design doc (linked in CL description).  I
prefer this over defining a new custom task and callback decl just to explicitly
declare ownership when NewRunnableMethod gives us that for free.  

Do you see another option not mentioned in the doc?

  public:
   // The Delegate services events that occur during the session requiring an
   // explicit (and session-global) action, as opposed to events that are simply
@@ -92,8 +93,19 @@ class SyncSession {
   // engine again.
   bool HasMoreToSync() const;
 
-  SyncSessionContext* context() { return context_; }
-  Delegate* delegate() { return delegate_; }
+  // Collects all state pertaining to how and why |s| originated and unions it
+  // with corresponding state in |this|, leaving |s| unchanged.  Allows |this|
+  // to take on the responsibilities |s| had (e.g. certain data types) in the
+  // next SyncShare operation using |this|, rather than needed two separate
+  // sessions.
+  void Coalesce(const SyncSession* s);
+
+  // Should be called any time |this| is being re-used in a new call to
+  // SyncShare (e.g., HasMoreToSync returned true).
+  void ResetTransientState();
+
+  SyncSessionContext* context() const { return context_; }
+  Delegate* delegate() const { return delegate_; }
   syncable::WriteTransaction* write_transaction() { return write_transaction_; }
   StatusController* status_controller() { return status_controller_.get(); }