Add a check that we make progress during incremental marking

src/incremental-marking.cc

 // Copyright 2012 the V8 project 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 "src/v8.h"
 
 #include "src/incremental-marking.h"
 
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 681 matching lines @@
     HeapObject* obj = marking_deque_.Pop();
 
     // Explicitly skip one word fillers. Incremental markbit patterns are
     // correct only for objects that occupy at least two words.
     Map* map = obj->map();
     if (map == filler_map) continue;
 
     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_);
+    // FIXME: remove after http://crbug.com/381820 is resolved.
+    CHECK(0 < delta && delta <= bytes_to_process);

[Hannes Payer (out of office), 2014/07/09 08:53:49]

delta can be larger than bytes_to_process. I guess the first check is fine to
guarantee progress.

+    bytes_to_process -= delta;
   }
 }
 
 
 void IncrementalMarking::ProcessMarkingDeque() {
   Map* filler_map = heap_->one_pointer_filler_map();
   while (!marking_deque_.IsEmpty()) {
     HeapObject* obj = marking_deque_.Pop();
 
     // Explicitly skip one word fillers. Incremental markbit patterns are
@@ skipping 273 matching lines @@
   bytes_scanned_ = 0;
   write_barriers_invoked_since_last_step_ = 0;
 }
 
 
 int64_t IncrementalMarking::SpaceLeftInOldSpace() {
   return heap_->MaxOldGenerationSize() - heap_->PromotedSpaceSizeOfObjects();
 }
 
 } }  // namespace v8::internal