anchor.diff:        if (value != null) {
           info.initializer = _constantToInfo[value];
         }
  +    }
  +
  +    if (JavaScriptBackend.TRACE_METHOD == 'post') {
  +      // We use element.hashCode because it is globally unique and it is
  +      // available while we are doing codegen.
  +      info.coverageId = '${element.hashCode}';
       }
   
       int closureSize = _addClosureInfo(info, element);
  
positive.code: 
      FieldInfo info = new FieldInfo(
          name: element.name,
          // We use element.hashCode because it is globally unique and it is
          // available while we are doing codegen.
          coverageId: '${element.hashCode}',
          type: '${element.type}',
          inferredType: '$inferredType',
          code: code,
  
negative.code:     FunctionInfo info = new FunctionInfo(
          name: name,
          functionKind: kind,
          modifiers: modifiers,
          returnType: returnType,
          inferredReturnType: inferredReturnType,
  