[turbofan] Move graph trimming functionality to dedicated GraphTrimmer.

src/compiler/node-marker.h

Index: src/compiler/node-marker.h
diff --git a/src/compiler/node-marker.h b/src/compiler/node-marker.h
index 9ce03b054b48a4167ca54e79ef9f03c96cf42cdf..5ef2063f18715cc5c59ddb9816f1de37c5ae2f1e 100644
--- a/src/compiler/node-marker.h
+++ b/src/compiler/node-marker.h
@@ -34,11 +34,10 @@ class NodeMarkerBase {
     DCHECK_LT(node->mark(), mark_max_);
     node->set_mark(mark + mark_min_);
   }
-  void Reset(Graph* graph);
 
  private:
-  Mark mark_min_;
-  Mark mark_max_;
+  Mark const mark_min_;
+  Mark const mark_max_;
 
   DISALLOW_COPY_AND_ASSIGN(NodeMarkerBase);
 };