Disable incremental marking when GC extension is exposed.

src/incremental-marking.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 335 matching lines @@
 
 bool IncrementalMarking::WorthActivating() {
 #ifndef DEBUG
   static const intptr_t kActivationThreshold = 8 * MB;
 #else
   // TODO(gc) consider setting this to some low level so that some
   // debug tests run with incremental marking and some without.
   static const intptr_t kActivationThreshold = 0;
 #endif
 
-  return FLAG_incremental_marking &&
+  return !FLAG_expose_gc &&
+      FLAG_incremental_marking &&
       !Serializer::enabled() &&
       heap_->PromotedSpaceSize() > kActivationThreshold;
 }
 
 
 void IncrementalMarking::ActivateGeneratedStub(Code* stub) {
   ASSERT(RecordWriteStub::GetMode(stub) ==
          RecordWriteStub::STORE_BUFFER_ONLY);
 
   if (!IsMarking()) {
@@ skipping 452 matching lines @@
   bytes_rescanned_ = 0;
   allocation_marking_factor_ = kInitialAllocationMarkingFactor;
 }
 
 
 int64_t IncrementalMarking::SpaceLeftInOldSpace() {
   return heap_->MaxOldGenerationSize() - heap_->PromotedSpaceSize();
 }
 
 } }  // namespace v8::internal