Why this CL triggers an OilPan crash.

content/browser/browsing_instance.cc

Index: content/browser/browsing_instance.cc
diff --git a/content/browser/browsing_instance.cc b/content/browser/browsing_instance.cc
index 5dd0ca4191fe832c5d4eea078c9cab946a8d397b..188b3351de346b60098860f031d9539cd269e723 100644
--- a/content/browser/browsing_instance.cc
+++ b/content/browser/browsing_instance.cc
@@ -15,10 +15,12 @@
 
 namespace content {
 
+int g_next_browsing_instance_id = 1;
+
 BrowsingInstance::BrowsingInstance(BrowserContext* browser_context)
     : browser_context_(browser_context),
-      active_contents_count_(0u) {
-}
+      active_contents_count_(0u),
+      browsing_instance_id_(g_next_browsing_instance_id++) {}
 
 bool BrowsingInstance::HasSiteInstance(const GURL& url) {
   std::string site =