[heap] Unify MarkingDeque push and unshift operations.

src/heap/incremental-marking-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_INCREMENTAL_MARKING_INL_H_
 #define V8_HEAP_INCREMENTAL_MARKING_INL_H_
 
 #include "src/heap/incremental-marking.h"
 
 namespace v8 {
@@ skipping 87 matching lines @@
       // order to finish off this marking phase.
       if (FLAG_trace_incremental_marking) {
         PrintIsolate(
             heap()->isolate(),
             "Hurrying incremental marking because of lack of progress\n");
       }
       marking_speed_ = kMaxMarkingSpeed;
     }
   }
 
-  heap_->mark_compact_collector()->marking_deque()->UnshiftGrey(obj);
+  heap_->mark_compact_collector()->marking_deque()->Unshift(obj);
 }
 
 
 void IncrementalMarking::WhiteToGreyAndPush(HeapObject* obj, MarkBit mark_bit) {
   Marking::WhiteToGrey(mark_bit);
-  heap_->mark_compact_collector()->marking_deque()->PushGrey(obj);
+  heap_->mark_compact_collector()->marking_deque()->Push(obj);
 }
 }
 }  // namespace v8::internal
 
 #endif  // V8_HEAP_INCREMENTAL_MARKING_INL_H_