Why this CL triggers an OilPan crash.

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 0dd62877d2ec961eacf4adb5fd4d41bd92ba66df..8b1a8eaead3498f9d0af62d7f41826d5ac1388ee 100644
--- a/content/browser/site_instance_impl.cc
+++ b/content/browser/site_instance_impl.cc
@@ -275,6 +275,10 @@ bool SiteInstanceImpl::HasRelatedSiteInstance(const GURL& url) {
   return browsing_instance_->HasSiteInstance(url);
 }
 
+int SiteInstanceImpl::GetBrowsingInstanceId() const {
+  return browsing_instance_->browsing_instance_id();
+}
+
 scoped_refptr<SiteInstance> SiteInstanceImpl::GetRelatedSiteInstance(
     const GURL& url) {
   return browsing_instance_->GetSiteInstanceForURL(url);