Simplify the write barrier.

src/incremental-marking.cc

Index: src/incremental-marking.cc
===================================================================
--- src/incremental-marking.cc	(revision 9979)
+++ src/incremental-marking.cc	(working copy)
@@ -223,12 +223,7 @@
   INLINE(void MarkObject(Object* obj)) {
     HeapObject* heap_object = HeapObject::cast(obj);
     MarkBit mark_bit = Marking::MarkBitFrom(heap_object);
-    if (mark_bit.data_only()) {
-      if (incremental_marking_->MarkBlackOrKeepGrey(mark_bit)) {
-        MemoryChunk::IncrementLiveBytes(heap_object->address(),
-                                        heap_object->Size());
-      }
-    } else if (Marking::IsWhite(mark_bit)) {
+    if (Marking::IsWhite(mark_bit)) {
       incremental_marking_->WhiteToGreyAndPush(heap_object, mark_bit);
     }
   }
@@ -261,15 +256,8 @@
 
     HeapObject* heap_object = HeapObject::cast(obj);
     MarkBit mark_bit = Marking::MarkBitFrom(heap_object);
-    if (mark_bit.data_only()) {
-      if (incremental_marking_->MarkBlackOrKeepGrey(mark_bit)) {
-          MemoryChunk::IncrementLiveBytes(heap_object->address(),
-                                          heap_object->Size());
-      }
-    } else {
-      if (Marking::IsWhite(mark_bit)) {
-        incremental_marking_->WhiteToGreyAndPush(heap_object, mark_bit);
-      }
+    if (Marking::IsWhite(mark_bit)) {
+      incremental_marking_->WhiteToGreyAndPush(heap_object, mark_bit);
     }
   }