Enable incremental marking when --expose-gc is turned on.

src/incremental-marking.cc

 // Copyright 2012 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 480 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
-  // Only start incremental marking in a safe state: 1) when expose GC is
-  // deactivated, 2) when incremental marking is turned on, 3) when we are
-  // currently not in a GC, and 4) when we are currently not serializing
-  // or deserializing the heap.
-  return !FLAG_expose_gc &&
-      FLAG_incremental_marking &&
+  // Only start incremental marking in a safe state: 1) when incremental
+  // marking is turned on, 2) when we are currently not in a GC, and
+  // 3) when we are currently not serializing or deserializing the heap.
+  return FLAG_incremental_marking &&
       FLAG_incremental_marking_steps &&
       heap_->gc_state() == Heap::NOT_IN_GC &&
       !Serializer::enabled() &&
       heap_->isolate()->IsInitialized() &&
       heap_->PromotedSpaceSizeOfObjects() > kActivationThreshold;
 }
 
 
 void IncrementalMarking::ActivateGeneratedStub(Code* stub) {
   ASSERT(RecordWriteStub::GetMode(stub) ==
@@ skipping 518 matching lines @@
   bytes_scanned_ = 0;
   write_barriers_invoked_since_last_step_ = 0;
 }
 
 
 int64_t IncrementalMarking::SpaceLeftInOldSpace() {
   return heap_->MaxOldGenerationSize() - heap_->PromotedSpaceSizeOfObjects();
 }
 
 } }  // namespace v8::internal