Purge session storage caches on memory pressure

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 eb65d82406992d4a33260b9048f502c92e3d6f2b..847b1930d706983b435a02c88edb0f7a6a448dc9 100644
--- a/content/browser/dom_storage/dom_storage_namespace.cc
+++ b/content/browser/dom_storage/dom_storage_namespace.cc
@@ -118,8 +118,8 @@ void DOMStorageNamespace::DeleteSessionStorageOrigin(const GURL& origin) {
 }
 
 void DOMStorageNamespace::PurgeMemory(bool aggressively) {
-  if (directory_.empty())
-    return;  // We can't purge w/o backing on disk.
+  if (namespace_id_ == kLocalStorageNamespaceId && directory_.empty())
+    return;  // We can't purge local storage w/o backing on disk.
 
   AreaMap::iterator it = areas_.begin();
   while (it != areas_.end()) {