sync: Implement per-type update processing

sync/sessions/sync_session_context.cc

Index: sync/sessions/sync_session_context.cc
diff --git a/sync/sessions/sync_session_context.cc b/sync/sessions/sync_session_context.cc
index 78b34427c937d8f337da172e5501f70c64660efb..d44591d79d852da92acded66ea8ac35475bec1f7 100644
--- a/sync/sessions/sync_session_context.cc
+++ b/sync/sessions/sync_session_context.cc
@@ -23,6 +23,7 @@ SyncSessionContext::SyncSessionContext(
     const std::string& invalidator_client_id)
     : connection_manager_(connection_manager),
       directory_(directory),
+      update_handler_deleter_(&update_handler_map_),
       commit_contributor_deleter_(&commit_contributor_map_),
       extensions_activity_(extensions_activity),
       notifications_enabled_(false),
@@ -50,14 +51,22 @@ void SyncSessionContext::set_routing_info(
   routing_info_ = routing_info;
 
   // TODO(rlarocque): This is not a good long-term solution.  We must find a
-  // better way to initialize the set of CommitContributors.
-  STLDeleteValues<CommitContributorMap>(&commit_contributor_map_);
+  // better way to initialize the set of CommitContributors and UpdateHandlers.
   ModelTypeSet enabled_types = GetRoutingInfoTypes(routing_info);
+
+  STLDeleteValues<CommitContributorMap>(&commit_contributor_map_);
   for (ModelTypeSet::Iterator it = enabled_types.First(); it.Good(); it.Inc()) {
     SyncDirectoryCommitContributor* contributor =
         new SyncDirectoryCommitContributor(directory(), it.Get());
     commit_contributor_map_.insert(std::make_pair(it.Get(), contributor));
   }
+
+  STLDeleteValues<UpdateHandlerMap>(&update_handler_map_);
+  for (ModelTypeSet::Iterator it = enabled_types.First(); it.Good(); it.Inc()) {
+    SyncDirectoryUpdateHandler* handler =
+        new SyncDirectoryUpdateHandler(directory(), it.Get());
+    update_handler_map_.insert(std::make_pair(it.Get(), handler));
+  }
 }
 
 }  // namespace sessions