[wip] Introduce SiteInstanceKeepAlive.

content/browser/site_instance_impl.cc

Index: content/browser/site_instance_impl.cc
diff --git a/content/browser/site_instance_impl.cc b/content/browser/site_instance_impl.cc
index e5a275c57d84e052ed002759e8b2ea92bbaf6550..b387c45f0028cbb3150598e6f5ba7f595a33cb17 100644
--- a/content/browser/site_instance_impl.cc
+++ b/content/browser/site_instance_impl.cc
@@ -19,6 +19,18 @@
 
 namespace content {
 
+SiteInstanceKeepAlive::SiteInstanceKeepAlive(
+    scoped_refptr<SiteInstanceImpl> instance)
+    : instance_(instance) {
+  instance_->increment_active_view_count();
+  instance_->GetProcess()->AddPendingView();
+}
+
+SiteInstanceKeepAlive::~SiteInstanceKeepAlive() {
+  instance_->GetProcess()->RemovePendingView();
+  instance_->decrement_active_view_count();
+}
+
 const RenderProcessHostFactory*
     SiteInstanceImpl::g_render_process_host_factory_ = NULL;
 int32 SiteInstanceImpl::next_site_instance_id_ = 1;
@@ -215,6 +227,10 @@ BrowserContext* SiteInstanceImpl::GetBrowserContext() const {
   return browsing_instance_->browser_context();
 }
 
+scoped_ptr<SiteInstanceKeepAlive> SiteInstanceImpl::AcquireKeepAlive() {
+  return make_scoped_ptr(new SiteInstanceKeepAlive(this));
+}
+
 /*static*/
 SiteInstance* SiteInstance::Create(BrowserContext* browser_context) {
   return new SiteInstanceImpl(new BrowsingInstance(browser_context));