Add isolate tag-profile and better handling of errors

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"
 
-class Isolate;
-
 namespace dart {
 
+class Isolate;
+class JSONObject;
+
 #define VM_TAG_LIST(V)                                                         \
+  V(Idle)                                                                      \
   V(VM) /* Catch all */                                                        \
   V(Compile)                                                                   \
   V(Script)                                                                    \
   V(GCNewSpace)                                                                \
   V(GCOldSpace)                                                                \
   V(RuntimeNative)                                                             \
-  V(Idle)                                                                      \
 
 
 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,
   };
 
   static const char* TagName(uword id);
 
  private:
   struct TagEntry {
     const char* name;
     uword id;
   };
   static TagEntry entries_[];
 };
 
+
 class VMTagScope : StackResource {
  public:
   VMTagScope(Isolate* isolate, uword tag);
   ~VMTagScope();
  private:
   uword previous_tag_;
 
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(VMTagScope);
 };
 
+
+class VMTagCounters {
+ public:
+  VMTagCounters();
+
+  void Increment(uword tag);
+
+  int64_t count(uword tag);
+
+  void PrintToJSONObject(JSONObject* obj);
+
+ private:
+  int64_t counters_[VMTag::kNumVMTags];
+};
+
 }  // namespace dart
 
 #endif  // VM_TAGS_H_