Allow to clear session and local storage when not backed on disk

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 72fae88fcedd3743a0f2d1707a6aa4a3f087975f..6f976f0d50158c387456251c8094c0ae19f9cb81 100644
--- a/content/browser/dom_storage/dom_storage_namespace.cc
+++ b/content/browser/dom_storage/dom_storage_namespace.cc
@@ -183,6 +183,13 @@ void DOMStorageNamespace::OnMemoryDump(
     it.second.area_->OnMemoryDump(pmd);
 }
 
+void DOMStorageNamespace::GetOriginsWithAreas(
+    std::vector<GURL>* origins) const {
+  origins->clear();
+  for (const auto& entry : areas_)
+    origins->push_back(entry.first);
+}
+
 DOMStorageNamespace::AreaHolder*
 DOMStorageNamespace::GetAreaHolder(const GURL& origin) {
   AreaMap::iterator found = areas_.find(origin);