Re-fix http://crbug.com/87176, and add a test.

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 56ee6df39d3493db582f3083348ec2754df04774..889d9d22b3fae0dd73520212f2a019e64ced97cb 100644
--- a/content/browser/site_instance_impl.cc
+++ b/content/browser/site_instance_impl.cc
@@ -35,12 +35,13 @@ static bool IsURLSameAsAnySiteInstance(const GURL& url) {
          url == GURL(kChromeUIShorthangURL);
 }
 
+const RenderProcessHostFactory*
+    SiteInstanceImpl::g_render_process_host_factory_ = NULL;
 int32 SiteInstanceImpl::next_site_instance_id_ = 1;
 
 SiteInstanceImpl::SiteInstanceImpl(BrowsingInstance* browsing_instance)
     : id_(next_site_instance_id_++),
       browsing_instance_(browsing_instance),
-      render_process_host_factory_(NULL),
       process_(NULL),
       has_site_(false) {
   DCHECK(browsing_instance);
@@ -111,8 +112,8 @@ RenderProcessHost* SiteInstanceImpl::GetProcess() {
 
     // Otherwise (or if that fails), create a new one.
     if (!process_) {
-      if (render_process_host_factory_) {
-        process_ = render_process_host_factory_->CreateRenderProcessHost(
+      if (g_render_process_host_factory_) {
+        process_ = g_render_process_host_factory_->CreateRenderProcessHost(
             browser_context);
       } else {
         StoragePartitionImpl* partition =
@@ -220,6 +221,11 @@ bool SiteInstanceImpl::HasWrongProcessForURL(const GURL& url) {
       GetProcess(), browsing_instance_->browser_context(), site_url);
 }
 
+void SiteInstanceImpl::set_render_process_host_factory(
+    const RenderProcessHostFactory* rph_factory) {
+  g_render_process_host_factory_ = rph_factory;
+}
+
 BrowserContext* SiteInstanceImpl::GetBrowserContext() const {
   return browsing_instance_->browser_context();
 }