[Sync] Implement MemoryDumpProvider.

components/sync/syncable/syncable_id.h

Index: components/sync/syncable/syncable_id.h
diff --git a/components/sync/syncable/syncable_id.h b/components/sync/syncable/syncable_id.h
index d847ea745280134760bac4df653093986432f13d..28e2b6b0b9359da70fae5f8211261acc5b4e702a 100644
--- a/components/sync/syncable/syncable_id.h
+++ b/components/sync/syncable/syncable_id.h
@@ -12,6 +12,7 @@
 #include <string>
 
 #include "base/containers/hash_tables.h"
+#include "base/trace_event/memory_usage_estimator.h"
 
 namespace base {
 class StringValue;
@@ -97,6 +98,10 @@ class Id {
   std::string s_;
 };
 
+inline size_t EstimateMemoryUsage(const Id& id) {
+  return base::trace_event::EstimateMemoryUsage(id.value());
+}
+
 }  // namespace syncable
 }  // namespace syncer