[turbofan] Do not set node's mark to min on get

src/compiler/node.h

 // Copyright 2013 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_COMPILER_NODE_H_
 #define V8_COMPILER_NODE_H_
 
 #include "src/compiler/opcodes.h"
 #include "src/compiler/operator.h"
 #include "src/compiler/types.h"
@@ skipping 276 matching lines @@
   void* operator new(size_t, void* location) { return location; }
 
   // Only NodeProperties should manipulate the op.
   void set_op(const Operator* op) { op_ = op; }
 
   // Only NodeProperties should manipulate the type.
   Type* type() const { return type_; }
   void set_type(Type* type) { type_ = type; }
 
   // Only NodeMarkers should manipulate the marks on nodes.
-  Mark mark() { return mark_; }
+  Mark mark() const { return mark_; }
   void set_mark(Mark mark) { mark_ = mark; }
 
   inline bool has_inline_inputs() const {
     return InlineCountField::decode(bit_field_) != kOutlineMarker;
   }
 
   void ClearInputs(int start, int count);
 
   typedef BitField<NodeId, 0, 24> IdField;
   typedef BitField<unsigned, 24, 4> InlineCountField;
@@ skipping 249 matching lines @@
 }
 
 
 Node::Uses::const_iterator Node::Uses::end() const { return const_iterator(); }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_NODE_H_