Refactor and cleanup VirtualMemory.

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 540 matching lines @@
 
 
 void IncrementalMarking::EnsureMarkingDequeIsCommitted() {
   if (marking_deque_memory_ == NULL) {
     marking_deque_memory_ = new VirtualMemory(4 * MB);
   }
   if (!marking_deque_memory_committed_) {
     bool success = marking_deque_memory_->Commit(
         reinterpret_cast<Address>(marking_deque_memory_->address()),
         marking_deque_memory_->size(),
-        false);  // Not executable.
+        VirtualMemory::NOT_EXECUTABLE);
     CHECK(success);
     marking_deque_memory_committed_ = true;
   }
 }
 
 
 void IncrementalMarking::UncommitMarkingDeque() {
   if (state_ == STOPPED && marking_deque_memory_committed_) {
     bool success = marking_deque_memory_->Uncommit(
         reinterpret_cast<Address>(marking_deque_memory_->address()),
@@ skipping 461 matching lines @@
   bytes_scanned_ = 0;
   write_barriers_invoked_since_last_step_ = 0;
 }
 
 
 int64_t IncrementalMarking::SpaceLeftInOldSpace() {
   return heap_->MaxOldGenerationSize() - heap_->PromotedSpaceSizeOfObjects();
 }
 
 } }  // namespace v8::internal