sync: Loop committing items without downloading updates (v2)

sync/sessions/ordered_commit_set.h

Index: sync/sessions/ordered_commit_set.h
diff --git a/sync/sessions/ordered_commit_set.h b/sync/sessions/ordered_commit_set.h
index 8551c070165f3fc36fdff468663618b4c9a35c37..f8e6938736b32dd3bdb4d5ce84a4f4ba7bd6c883 100644
--- a/sync/sessions/ordered_commit_set.h
+++ b/sync/sessions/ordered_commit_set.h
@@ -64,14 +64,17 @@ class OrderedCommitSet {
   // belonging to |group|.  This is useful when you need to process a commit
   // response one ModelSafeGroup at a time. See GetCommitIdAt for how the
   // indices contained in the returned Projection can be used.
-  const Projection& GetCommitIdProjection(browser_sync::ModelSafeGroup group) {
-    return projections_[group];
-  }
+  const Projection& GetCommitIdProjection(
+      browser_sync::ModelSafeGroup group) const;
 
-  int Size() const {
+  size_t Size() const {
     return commit_ids_.size();
   }
 
+  bool Empty() const {
+    return Size() == 0;
+  }
+
   // Returns true iff any of the commit ids added to this set have model type
   // BOOKMARKS.
   bool HasBookmarkCommitId() const;
@@ -80,6 +83,9 @@ class OrderedCommitSet {
   void AppendReverse(const OrderedCommitSet& other);
   void Truncate(size_t max_size);
 
+  // Removes all entries from this set.
+  void Clear();
+
   void operator=(const OrderedCommitSet& other);
  private:
   // A set of CommitIdProjections associated with particular ModelSafeGroups.
@@ -92,7 +98,7 @@ class OrderedCommitSet {
     syncable::ModelType group;
   };
 
-  CommitItem GetCommitItemAt(const int position) const;
+  CommitItem GetCommitItemAt(const size_t position) const;
 
   // These lists are different views of the same items; e.g they are
   // isomorphic.