Persist sessionStorage on disk.

content/browser/dom_storage/dom_storage_context_impl.cc

Index: content/browser/dom_storage/dom_storage_context_impl.cc
diff --git a/content/browser/dom_storage/dom_storage_context_impl.cc b/content/browser/dom_storage/dom_storage_context_impl.cc
index d525462ee2ab28b0ab892fc5520086d7e1ffcada..f3f1b63c0985325d86af7c510f89f68050025406 100644
--- a/content/browser/dom_storage/dom_storage_context_impl.cc
+++ b/content/browser/dom_storage/dom_storage_context_impl.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/command_line.h"
 #include "base/file_path.h"
 #include "base/message_loop_proxy.h"
 #include "content/browser/dom_storage/session_storage_namespace_impl.h"
@@ -24,6 +25,7 @@ using dom_storage::DomStorageWorkerPoolTaskRunner;
 namespace {
 
 const char kLocalStorageDirectory[] = "Local Storage";
+const char kSessionStorageDirectory[] = "Session Storage";
 
 void InvokeUsageInfoCallbackHelper(
       const DOMStorageContext::GetUsageInfoCallback& callback,
@@ -50,12 +52,16 @@ DOMStorageContextImpl::DOMStorageContextImpl(
     const FilePath& data_path,
     quota::SpecialStoragePolicy* special_storage_policy) {
   base::SequencedWorkerPool* worker_pool = BrowserThread::GetBlockingPool();
-  // TODO(marja): Pass a nonempty session storage directory when session storage
-  // is backed on disk.
+  // TODO(marja): Remove this as soon as the sessionStorage on disk
+  // implementation is on by default.
+  const char kEnableRestoreSessionState[] = "enable-restore-session-state";
+  bool session_storage_on_disk =
+      CommandLine::ForCurrentProcess()->HasSwitch(kEnableRestoreSessionState);
   context_ = new dom_storage::DomStorageContext(
       data_path.empty() ?
           data_path : data_path.AppendASCII(kLocalStorageDirectory),
-      FilePath(),  // Empty session storage directory.
+      (data_path.empty() || !session_storage_on_disk) ?
+          FilePath() : data_path.AppendASCII(kSessionStorageDirectory),
       special_storage_policy,
       new DomStorageWorkerPoolTaskRunner(
           worker_pool,
@@ -92,6 +98,10 @@ DOMStorageContextImpl::RecreateSessionStorage(
       new SessionStorageNamespaceImpl(this, persistent_id));
 }
 
+void DOMStorageContextImpl::StartScavengingUnusedSessionStorage() {
+  context_->StartScavengingUnusedSessionStorage();
+}
+
 void DOMStorageContextImpl::PurgeMemory() {
   DCHECK(context_);
   context_->task_runner()->PostShutdownBlockingTask(