Add support for enabling DCHECKs in release mode

src/heap/mark-compact.cc

Index: src/heap/mark-compact.cc
diff --git a/src/heap/mark-compact.cc b/src/heap/mark-compact.cc
index 27d257980f281c9067d264f8e239bda5d198a481..33a8ae8b7e6b5518c46f461b428faa921af0d6e0 100644
--- a/src/heap/mark-compact.cc
+++ b/src/heap/mark-compact.cc
@@ -37,7 +37,7 @@ const char* Marking::kImpossibleBitPattern = "01";
 
 MarkCompactCollector::MarkCompactCollector(Heap* heap)
     :  // NOLINT
-#ifdef DEBUG
+#if DCHECK_IS_ON
       state_(IDLE),
 #endif
       reduce_memory_footprint_(false),
@@ -543,7 +543,7 @@ void Marking::TransferMark(Address old_start, Address new_start) {
   MarkBit new_mark_bit = MarkBitFrom(new_start);
   MarkBit old_mark_bit = MarkBitFrom(old_start);
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   ObjectColor old_color = Color(old_mark_bit);
 #endif
 
@@ -561,7 +561,7 @@ void Marking::TransferMark(Address old_start, Address new_start) {
     heap_->incremental_marking()->RestartIfNotMarking();
   }
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   ObjectColor new_color = Color(new_mark_bit);
   DCHECK(new_color == old_color);
 #endif
@@ -815,7 +815,7 @@ void MarkCompactCollector::AbortCompaction() {
 void MarkCompactCollector::Prepare() {
   was_marked_incrementally_ = heap()->incremental_marking()->IsMarking();
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   DCHECK(state_ == IDLE);
   state_ = PREPARE_GC;
 #endif
@@ -858,7 +858,7 @@ void MarkCompactCollector::Prepare() {
 
 
 void MarkCompactCollector::Finish() {
-#ifdef DEBUG
+#if DCHECK_IS_ON
   DCHECK(state_ == SWEEP_SPACES || state_ == RELOCATE_OBJECTS);
   state_ = IDLE;
 #endif
@@ -1298,7 +1298,7 @@ class MarkCompactMarkingVisitor
   // Visit an unmarked object.
   INLINE(static void VisitUnmarkedObject(MarkCompactCollector* collector,
                                          HeapObject* obj)) {
-#ifdef DEBUG
+#if DCHECK_IS_ON

[Jakob Kummerow, 2014/12/03 10:53:53]

just drop this #if

     DCHECK(collector->heap()->Contains(obj));
     DCHECK(!collector->heap()->mark_compact_collector()->IsMarked(obj));
 #endif
@@ -2180,7 +2180,7 @@ void MarkCompactCollector::MarkLiveObjects() {
     InitializeMarkingDeque();
   }
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   DCHECK(state_ == PREPARE_GC);
   state_ = MARK_LIVE_OBJECTS;
 #endif
@@ -4155,7 +4155,7 @@ void MarkCompactCollector::SweepSpaces() {
     start_time = base::OS::TimeCurrentMillis();
   }
 
-#ifdef DEBUG
+#if DCHECK_IS_ON
   state_ = SWEEP_SPACES;
 #endif
   MoveEvacuationCandidatesToEndOfPagesList();