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

components/sync_driver/glue/sync_backend_host_core.cc

Index: components/sync_driver/glue/sync_backend_host_core.cc
diff --git a/components/sync_driver/glue/sync_backend_host_core.cc b/components/sync_driver/glue/sync_backend_host_core.cc
index af99ecac4015ba7fba38c70d26d1f9c00d5cee48..7282b8712b4d537dc869545babc4091f3d1b7d7d 100644
--- a/components/sync_driver/glue/sync_backend_host_core.cc
+++ b/components/sync_driver/glue/sync_backend_host_core.cc
@@ -10,6 +10,7 @@
 #include "base/files/file_util.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
+#include "base/trace_event/memory_dump_manager.h"
 #include "components/data_use_measurement/core/data_use_user_data.h"
 #include "components/invalidation/public/invalidation_util.h"
 #include "components/invalidation/public/object_id_invalidation_map.h"
@@ -129,6 +130,16 @@ SyncBackendHostCore::~SyncBackendHostCore() {
   DCHECK(!sync_manager_.get());
 }
 
+bool SyncBackendHostCore::OnMemoryDump(
+    const base::trace_event::MemoryDumpArgs& args,
+    base::trace_event::ProcessMemoryDump* pmd) {
+  DCHECK_EQ(base::MessageLoop::current(), sync_loop_);
+  if (!sync_manager_)
+    return false;
+  sync_manager_->OnMemoryDump(pmd);
+  return true;
+}
+
 void SyncBackendHostCore::OnSyncCycleCompleted(
     const syncer::sessions::SyncSessionSnapshot& snapshot) {
   if (!sync_loop_)
@@ -459,6 +470,8 @@ void SyncBackendHostCore::DoInitialize(
   args.cancelation_signal = &stop_syncing_signal_;
   args.saved_nigori_state = std::move(options->saved_nigori_state);
   sync_manager_->Init(&args);
+  base::trace_event::MemoryDumpManager::GetInstance()->RegisterDumpProvider(
+      this, "SyncDirectory", sync_loop_->task_runner());
 }
 
 void SyncBackendHostCore::DoUpdateCredentials(
@@ -575,6 +588,9 @@ void SyncBackendHostCore::DoShutdown(syncer::ShutdownReason reason) {
 
 void SyncBackendHostCore::DoDestroySyncManager(syncer::ShutdownReason reason) {
   DCHECK(sync_loop_->task_runner()->BelongsToCurrentThread());
+
+  base::trace_event::MemoryDumpManager::GetInstance()->UnregisterDumpProvider(
+      this);
   if (sync_manager_) {
     DisableDirectoryTypeDebugInfoForwarding();
     save_changes_timer_.reset();