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

components/sync_driver/glue/sync_backend_host_core.h

Index: components/sync_driver/glue/sync_backend_host_core.h
diff --git a/components/sync_driver/glue/sync_backend_host_core.h b/components/sync_driver/glue/sync_backend_host_core.h
index d93d4192e683470d5c97ba6101ed2cc37dd6572c..da0bad3b4ae6339e61da92e84d4c13d8231f2dfd 100644
--- a/components/sync_driver/glue/sync_backend_host_core.h
+++ b/components/sync_driver/glue/sync_backend_host_core.h
@@ -14,6 +14,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/timer/timer.h"
+#include "base/trace_event/memory_dump_provider.h"
 #include "components/invalidation/public/invalidation.h"
 #include "components/sync_driver/glue/sync_backend_host_impl.h"
 #include "components/sync_driver/system_encryptor.h"
@@ -94,6 +95,7 @@ struct DoConfigureSyncerTypes {
 
 class SyncBackendHostCore
     : public base::RefCountedThreadSafe<SyncBackendHostCore>,
+      public base::trace_event::MemoryDumpProvider,
       public syncer::SyncEncryptionHandler::Observer,
       public syncer::SyncManager::Observer,
       public syncer::TypeDebugInfoObserver {
@@ -103,6 +105,10 @@ class SyncBackendHostCore
        bool has_sync_setup_completed,
        const base::WeakPtr<SyncBackendHostImpl>& backend);
 
+  // MemoryDumpProvider implementation.
+  bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
+                    base::trace_event::ProcessMemoryDump* pmd) override;
+
   // SyncManager::Observer implementation.  The Core just acts like an air
   // traffic controller here, forwarding incoming messages to appropriate
   // landing threads.