[tracing] Add a memory dump provider for DOM storage

content/browser/dom_storage/session_storage_database.h

Index: content/browser/dom_storage/session_storage_database.h
diff --git a/content/browser/dom_storage/session_storage_database.h b/content/browser/dom_storage/session_storage_database.h
index 7ca2da71846f9198c9f80912e899151fdfafa417..81c631337a5fdd0f37190dcb5025ac5919124cdf 100644
--- a/content/browser/dom_storage/session_storage_database.h
+++ b/content/browser/dom_storage/session_storage_database.h
@@ -27,6 +27,12 @@ struct ReadOptions;
 class WriteBatch;
 }  // namespace leveldb
 
+namespace base {
+namespace trace_event {
+class ProcessMemoryDump;
+}
+}
+
 namespace content {
 
 // SessionStorageDatabase holds the data from multiple namespaces and multiple
@@ -75,6 +81,9 @@ class CONTENT_EXPORT SessionStorageDatabase :
   bool ReadNamespacesAndOrigins(
       std::map<std::string, std::vector<GURL> >* namespaces_and_origins);
 
+  // Adds memory statistics to |pmd| for chrome://tracing.
+  void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd);
+
  private:
   friend class base::RefCountedThreadSafe<SessionStorageDatabase>;
   class DBOperation;