[tracing] Add a memory dump provider for DOM storage

content/browser/dom_storage/dom_storage_namespace.cc

Index: content/browser/dom_storage/dom_storage_namespace.cc
diff --git a/content/browser/dom_storage/dom_storage_namespace.cc b/content/browser/dom_storage/dom_storage_namespace.cc
index a8681b6e6c2b148491689f6c47b543172dbab08d..72fae88fcedd3743a0f2d1707a6aa4a3f087975f 100644
--- a/content/browser/dom_storage/dom_storage_namespace.cc
+++ b/content/browser/dom_storage/dom_storage_namespace.cc
@@ -176,6 +176,13 @@ unsigned int DOMStorageNamespace::CountInMemoryAreas() const {
   return area_count;
 }
 
+void DOMStorageNamespace::OnMemoryDump(
+    base::trace_event::ProcessMemoryDump* pmd) {
+  DCHECK(task_runner_->IsRunningOnPrimarySequence());
+  for (const auto& it : areas_)
+    it.second.area_->OnMemoryDump(pmd);
+}
+
 DOMStorageNamespace::AreaHolder*
 DOMStorageNamespace::GetAreaHolder(const GURL& origin) {
   AreaMap::iterator found = areas_.find(origin);