Why this CL triggers an OilPan crash.

content/browser/browsing_instance.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/browsing_instance.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "content/browser/site_instance_impl.h"
 #include "content/common/site_isolation_policy.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/common/content_switches.h"
 #include "content/public/common/url_constants.h"
 
 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 =
       SiteInstanceImpl::GetSiteForURL(browser_context_, url)
           .possibly_invalid_spec();
 
   return site_instance_map_.find(site) != site_instance_map_.end();
 }
 
 scoped_refptr<SiteInstanceImpl> BrowsingInstance::GetSiteInstanceForURL(
@@ skipping 71 matching lines @@
 }
 
 BrowsingInstance::~BrowsingInstance() {
   // We should only be deleted when all of the SiteInstances that refer to
   // us are gone.
   DCHECK(site_instance_map_.empty());
   DCHECK_EQ(0u, active_contents_count_);
 }
 
 }  // namespace content