[Sync] Rely on directory to decide which types need to be purged

sync/syncable/directory.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sync/syncable/directory.h"
 
 #include <iterator>
 
 #include "base/base64.h"
 #include "base/debug/trace_event.h"
@@ skipping 40 matching lines @@
     ModelType model_type) {
   // Clear everything except the data type id field.
   download_progress[model_type].Clear();
   download_progress[model_type].set_data_type_id(
       GetSpecificsFieldNumberFromModelType(model_type));
 
   // Explicitly set an empty token field to denote no progress.
   download_progress[model_type].set_token("");
 }
 
+bool Directory::PersistedKernelInfo::HasEmptyDownloadProgress(
+    ModelType model_type) {
+  const sync_pb::DataTypeProgressMarker& progress_marker =
+      download_progress[model_type];
+  return progress_marker.token().empty();
+}
+
 Directory::SaveChangesSnapshot::SaveChangesSnapshot()
     : kernel_info_status(KERNEL_SHARE_INFO_INVALID) {
 }
 
 Directory::SaveChangesSnapshot::~SaveChangesSnapshot() {
   STLDeleteElements(&dirty_metas);
   STLDeleteElements(&delete_journals);
 }
 
 Directory::Kernel::Kernel(
@@ skipping 660 matching lines @@
 
   {
     WriteTransaction trans(FROM_HERE, PURGE_ENTRIES, this);
 
     EntryKernelSet entries_to_journal;
     STLElementDeleter<EntryKernelSet> journal_deleter(&entries_to_journal);
 
     {
       ScopedKernelLock lock(this);
 
+      bool found_progress = false;
+      for (ModelTypeSet::Iterator iter = disabled_types.First(); iter.Good();
+           iter.Inc()) {
+        if (!kernel_->persisted_info.HasEmptyDownloadProgress(iter.Get()))
+          found_progress = true;
+      }
+
+      // If none of the disabled types have progress markers, there's nothing to
+      // purge.
+      if (!found_progress)
+        return true;
+
       // We iterate in two passes to avoid a bug in STLport (which is used in
       // the Android build).  There are some versions of that library where a
       // hash_map's iterators can be invalidated when an item is erased from the
       // hash_map.
       // See http://sourceforge.net/p/stlport/bugs/239/.
 
       std::set<EntryKernel*> to_purge;
       for (MetahandlesMap::iterator it = kernel_->metahandles_map.begin();
            it != kernel_->metahandles_map.end(); ++it) {
         const sync_pb::EntitySpecifics& local_specifics =
@@ skipping 695 matching lines @@
   }
 }
 
 void Directory::UnmarkDirtyEntry(WriteTransaction* trans, Entry* entry) {
   CHECK(trans);
   entry->kernel_->clear_dirty(&kernel_->dirty_metahandles);
 }
 
 }  // namespace syncable
 }  // namespace syncer