GTTF: Enable glibcxx debug mode for Debug builds by default.

content/browser/loader/resource_scheduler.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/loader/resource_scheduler.h"
 
 #include "base/stl_util.h"
 #include "content/common/resource_messages.h"
 #include "content/browser/loader/resource_message_delegate.h"
 #include "content/public/browser/resource_controller.h"
@@ skipping 356 matching lines @@
 
   while (!request_iter.is_null()) {
     ScheduledResourceRequest* request = request_iter.value();
     ShouldStartReqResult query_result = ShouldStartRequest(request, client);
 
     if (query_result == START_REQUEST) {
       client->pending_requests.Erase(request);
       StartRequest(request, client);
 
       // StartRequest can modify the pending list, so we (re)start evaluation
-      // from the currently highest priority request.
+      // from the currently highest priority request. Avoid copying a singular
+      // iterator, which would trigger undefined behavior.
+      if (client->pending_requests.GetNextHighestIterator().is_null())
+        break;
       request_iter = client->pending_requests.GetNextHighestIterator();
     } else if (query_result == DO_NOT_START_REQUEST_AND_KEEP_SEARCHING) {
       ++request_iter;
       continue;
     } else {
       DCHECK(query_result == DO_NOT_START_REQUEST_AND_STOP_SEARCHING);
       break;
     }
   }
 }
@@ skipping 102 matching lines @@
 
   return START_REQUEST;
 }
 
 ResourceScheduler::ClientId ResourceScheduler::MakeClientId(
     int child_id, int route_id) {
   return (static_cast<ResourceScheduler::ClientId>(child_id) << 32) | route_id;
 }
 
 }  // namespace content