[WIP][tracing] Add memory dump provider for sync Directory

sync/internal_api/public/sync_manager.h

Index: sync/internal_api/public/sync_manager.h
diff --git a/sync/internal_api/public/sync_manager.h b/sync/internal_api/public/sync_manager.h
index 1e9cb34b2a4bdeda4f5e0f8305eb690cab2603e1..8e8d7d926a96a1353f1eeafcc3265df664fdd4f3 100644
--- a/sync/internal_api/public/sync_manager.h
+++ b/sync/internal_api/public/sync_manager.h
@@ -37,6 +37,12 @@
 
 class GURL;
 
+namespace base {
+namespace trace_event {
+class ProcessMemoryDump;
+}
+}
+
 namespace sync_pb {
 class EncryptedData;
 }  // namespace sync_pb
@@ -344,6 +350,9 @@ class SYNC_EXPORT SyncManager {
   // Status-related getter.  May be called on any thread.
   virtual SyncStatus GetDetailedStatus() const = 0;
 
+  // Adds memory usage statistics to |pmd| for chrome://tracing.
+  virtual void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd) = 0;
+
   // Call periodically from a database-safe thread to persist recent changes
   // to the syncapi model.
   virtual void SaveChanges() = 0;