Add a check that we make progress during incremental marking

BUG=381820
R=hpayer@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/382463002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22294 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/incremental-marking.cc

@@ -699,7 +699,10 @@ void IncrementalMarking::ProcessMarkingDeque(intptr_t bytes_to_process) {
     int size = obj->SizeFromMap(map);
     unscanned_bytes_of_large_object_ = 0;
     VisitObject(map, obj, size);
-    bytes_to_process -= (size - unscanned_bytes_of_large_object_);
+    int delta = (size - unscanned_bytes_of_large_object_);
+    // TODO(jochen): remove after http://crbug.com/381820 is resolved.
+    CHECK_LT(0, delta);
+    bytes_to_process -= delta;
   }
 }