dart2js: Use frequency of occurence to sort metadata indices.

pkg/compiler/lib/src/ssa/codegen_helpers.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 /**
  * Replaces some instructions with specialized versions to make codegen easier.
  * Caches codegen information on nodes.
  */
@@ skipping 102 matching lines @@
       Selector selector = node.selector;
       if (backend.isInterceptedSelector(selector) &&
           !backend.isInterceptedMixinSelector(selector)) {
         HInstruction interceptor = node.inputs[0];
         HInstruction receiverArgument = node.inputs[1];
 
         if (interceptor.nonCheck() == receiverArgument.nonCheck()) {
           // TODO(15933): Make automatically generated property extraction
           // closures work with the dummy receiver optimization.
           if (!selector.isGetter) {
-            ConstantValue constant = new DummyConstantValue(
+            ConstantValue constant = new SyntheticConstantValue(
+                SyntheticConstantKind.DUMMY_RECEIVER,
                 receiverArgument.instructionType);
             HConstant dummy = graph.addConstant(constant, compiler);
             receiverArgument.usedBy.remove(node);
             node.inputs[1] = dummy;
             dummy.usedBy.add(node);
           }
         }
       }
     }
 
@@ skipping 623 matching lines @@
     }
 
     // If [thenInput] is defined in the first predecessor, then it is only used
     // by [phi] and can be generated at use site.
     if (identical(thenInput.block, end.predecessors[0])) {
       assert(thenInput.usedBy.length == 1);
       markAsGenerateAtUseSite(thenInput);
     }
   }
 }