[tracing] Add a memory dump provider for DOM storage

content/browser/dom_storage/dom_storage_area.h

Index: content/browser/dom_storage/dom_storage_area.h
diff --git a/content/browser/dom_storage/dom_storage_area.h b/content/browser/dom_storage/dom_storage_area.h
index 4e91b605fe37880cd1c986bdd7fb90de71e8b071..5ad31a687bcc43f4af53280ccc087122ca13ff9d 100644
--- a/content/browser/dom_storage/dom_storage_area.h
+++ b/content/browser/dom_storage/dom_storage_area.h
@@ -21,6 +21,12 @@
 #include "content/common/dom_storage/dom_storage_types.h"
 #include "url/gurl.h"
 
+namespace base {
+namespace trace_event {
+class ProcessMemoryDump;
+}
+}
+
 namespace content {
 
 class DOMStorageDatabaseAdapter;
@@ -96,6 +102,9 @@ class CONTENT_EXPORT DOMStorageArea
   // Returns true if the data is loaded in memory.
   bool IsLoadedInMemory() const { return is_initial_import_done_; }
 
+  // Adds memory usage statistics to ProcessMemoryDump object for tracing.
+  void OnMemoryDump(base::trace_event::ProcessMemoryDump* pmd);
+
  private:
   friend class DOMStorageAreaTest;
   FRIEND_TEST_ALL_PREFIXES(DOMStorageAreaTest, DOMStorageAreaBasics);