[tracing] Show the local storage databases under dom_storage

content/browser/dom_storage/dom_storage_database_adapter.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_DATABASE_ADAPTER_H_
 #define CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_DATABASE_ADAPTER_H_
 
 // Database interface used by DOMStorageArea. Abstracts the differences between
 // the per-origin DOMStorageDatabases for localStorage and
 // SessionStorageDatabase which stores multiple origins.
 
+#include <string>
+
 #include "content/common/content_export.h"
 #include "content/common/dom_storage/dom_storage_types.h"
 
+namespace base {
+namespace trace_event {
+class ProcessMemoryDump;
+}
+}
+
 namespace content {
 
 class CONTENT_EXPORT DOMStorageDatabaseAdapter {
  public:
   virtual ~DOMStorageDatabaseAdapter() {}
   virtual void ReadAllValues(DOMStorageValuesMap* result) = 0;
   virtual bool CommitChanges(
       bool clear_all_first, const DOMStorageValuesMap& changes) = 0;
   virtual void DeleteFiles() {}
   virtual void Reset() {}
+  // Adds memory statistics to |pmd| object for tracing.
+  virtual void ReportMemoryUsage(base::trace_event::ProcessMemoryDump* pmd,
+                                 const std::string& name) {}
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_DOM_STORAGE_DOM_STORAGE_DATABASE_ADAPTER_H_