[Sync] Implement MemoryDumpProvider.

components/sync/syncable/directory.h

Index: components/sync/syncable/directory.h
diff --git a/components/sync/syncable/directory.h b/components/sync/syncable/directory.h
index 4fb0240922be4b47e3facb77e9d51bde9653371f..461892b9d2af02b65106e9d261a08925b912433e 100644
--- a/components/sync/syncable/directory.h
+++ b/components/sync/syncable/directory.h
@@ -30,6 +30,12 @@
 #include "components/sync/syncable/parent_child_index.h"
 #include "components/sync/syncable/syncable_delete_journal.h"
 
+namespace base {
+namespace trace_event {
+class ProcessMemoryDump;
+}
+}
+
 namespace syncer {
 
 class Cryptographer;
@@ -95,6 +101,8 @@ class Directory {
     // Whether a valid progress marker exists for |model_type|.
     bool HasEmptyDownloadProgress(ModelType model_type);
 
+    size_t EstimateMemoryUsage() const;
+
     // Last sync timestamp fetched from the server.
     sync_pb::DataTypeProgressMarker download_progress[MODEL_TYPE_COUNT];
     // Sync-side transaction version per data type. Monotonically incremented
@@ -281,6 +289,9 @@ class Directory {
   // Gets the total number of entries in the directory.
   size_t GetEntriesCount() const;
 
+  // Adds memory statistics to |pmd| for chrome://tracing.
+  void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd);
+
   // Gets/Increments transaction version of a model type. Must be called when
   // holding kernel mutex.
   int64_t GetTransactionVersion(ModelType type) const;