sync: Implement per-type update processing

Introduces a new class that represents a syncable::Directory's udpate
requesting and processing capabilities.  The intention is that this will
eventually be expanded to cover commits as well.  Eventually, this will
be used as the basis for an interface between sync and 

Some update logic has been moved into this SyncDirectoryUpdateHandler
class or download.cc.  The rest of it can be found in
process_update_util.cc, the successor to the old ProcessUpdatesCommand.
The StoreTimestampsCommand has been entirely removed.  The unit tests
associated with these SyncerCommands have been ported to
sync_directory_update_handler_unittest.cc.

Except for a few error scenarios that are now handled differently, the
observable behavior of the client should not be changed by this CL.

BUG=278484

Review URL: https://codereview.chromium.org/38803003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231878 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 24 insertions, 2 deletions

diff --git a/sync/sessions/sync_session_context.cc b/sync/sessions/sync_session_context.cc
index 78b3442..d44591d 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
diff --git a/sync/sessions/sync_session_context.h b/sync/sessions/sync_session_context.h
index 3133c32..d195943 100644
--- a/sync/sessions/sync_session_context.h
+++ b/sync/sessions/sync_session_context.h
@@ -25,6 +25,7 @@
 #include "base/stl_util.h"
 #include "sync/base/sync_export.h"
 #include "sync/engine/sync_directory_commit_contributor.h"
+#include "sync/engine/sync_directory_update_handler.h"
 #include "sync/engine/sync_engine_event.h"
 #include "sync/engine/syncer_types.h"
 #include "sync/engine/traffic_recorder.h"
@@ -75,6 +76,10 @@ class SYNC_EXPORT_PRIVATE SyncSessionContext {
 
   void set_routing_info(const ModelSafeRoutingInfo& routing_info);
 
+  UpdateHandlerMap* update_handler_map() {
+    return &update_handler_map_;
+  }
+
   CommitContributorMap* commit_contributor_map() {
     return &commit_contributor_map_;
   }
@@ -158,6 +163,14 @@ class SYNC_EXPORT_PRIVATE SyncSessionContext {
   // Must be updated manually when SBR's state is modified.
   ModelSafeRoutingInfo routing_info_;
 
+  // A map of 'update handlers', one for each enabled type.
+  // This must be kept in sync with the routing info.  Our temporary solution to
+  // that problem is to initialize this map in set_routing_info().
+  UpdateHandlerMap update_handler_map_;
+
+  // Deleter for the |update_handler_map_|.
+  STLValueDeleter<UpdateHandlerMap> update_handler_deleter_;
+
   // A map of 'commit contributors', one for each enabled type.
   // This must be kept in sync with the routing info.  Our temporary solution to
   // that problem is to initialize this map in set_routing_info().