Refactor 'dart:profiler' UserTag API

runtime/vm/profiler.h

 // Copyright (c) 2013, 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.
 
 #ifndef VM_PROFILER_H_
 #define VM_PROFILER_H_
 
 #include "vm/allocation.h"
 #include "vm/code_observers.h"
 #include "vm/globals.h"
@@ skipping 103 matching lines @@
 
 // Each Sample holds a stack trace from an isolate.
 class Sample {
  public:
   void Init(Isolate* isolate, int64_t timestamp, ThreadId tid) {
     timestamp_ = timestamp;
     tid_ = tid;
     isolate_ = isolate;
     pc_marker_ = 0;
     vm_tag_ = VMTag::kInvalidTagId;
-    user_tag_ = UserTags::kNoUserTag;
+    user_tag_ = UserTags::kDefaultUserTag;
     sp_ = 0;
     fp_ = 0;
     state_ = 0;
     for (intptr_t i = 0; i < kSampleFramesSize; i++) {
       pcs_[i] = 0;
     }
   }
 
   // Isolate sample was taken from.
   Isolate* isolate() const {
@@ skipping 162 matching lines @@
   intptr_t capacity_;
   uintptr_t cursor_;
 
   DISALLOW_COPY_AND_ASSIGN(SampleBuffer);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_PROFILER_H_