Purge session storage caches on memory pressure

content/browser/dom_storage/dom_storage_namespace.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/dom_storage/dom_storage_namespace.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "content/browser/dom_storage/dom_storage_area.h"
@@ skipping 100 matching lines @@
   }
 }
 
 void DOMStorageNamespace::DeleteSessionStorageOrigin(const GURL& origin) {
   DOMStorageArea* area = OpenStorageArea(origin);
   area->FastClear();
   CloseStorageArea(area);
 }
 
 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()) {
     const AreaHolder& holder = it->second;
 
     // We can't purge if there are changes pending.
     if (holder.area_->HasUncommittedChanges()) {
       if (holder.open_count_ == 0) {
          // Schedule an immediate commit so the next time we're asked to purge,
          // we can drop it from memory.
@@ skipping 81 matching lines @@
     DOMStorageArea* area, int count)
     : area_(area), open_count_(count) {
 }
 
 DOMStorageNamespace::AreaHolder::AreaHolder(const AreaHolder& other) = default;
 
 DOMStorageNamespace::AreaHolder::~AreaHolder() {
 }
 
 }  // namespace content