Enable native stack walking for allocation profiling

runtime/vm/tags.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_TAGS_H_
 #define VM_TAGS_H_
 
 #include "vm/allocation.h"
 
 namespace dart {
@@ skipping 23 matching lines @@
 
 class VMTag : public AllStatic {
  public:
   enum VMTagId {
     kInvalidTagId = 0,
 #define DEFINE_VM_TAG_ID(tag)                                                  \
     k##tag##TagId,
     VM_TAG_LIST(DEFINE_VM_TAG_ID)
 #undef DEFINE_VM_TAG_KIND
     kNumVMTags,
+    //
+    // All tags below |kNumVMTags| are special meta-data tags and do not
+    // indicate the state of the VM during a sample.
+    //
     kRootTagId,       // Special tag used as root of all profiles.
     kTruncatedTagId,  // Special tag used to indicate a truncated call stack.
-    // ProfileInfo tags.
+    // Code transition tags (used by unit tests).
     kNoneCodeTagId,
     kOptimizedCodeTagId,
     kUnoptimizedCodeTagId,
     kNativeCodeTagId,
     kInlineStartCodeTagId,
     kInlineEndCodeTagId,
     kLastTagId,
   };
 
   static bool IsVMTag(uword id) {
@@ skipping 53 matching lines @@
   static bool IsUserTag(uword tag_id) {
     return (tag_id >= kUserTagIdOffset) &&
            (tag_id < kUserTagIdOffset + kMaxUserTags);
   }
 };
 
 
 }  // namespace dart
 
 #endif  // VM_TAGS_H_