Add --print-metrics vm flag for printing metrics to console

runtime/vm/metrics.h

 // Copyright (c) 2014, 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_METRICS_H_
 #define VM_METRICS_H_
 
 #include "vm/allocation.h"
 
 namespace dart {
@@ skipping 17 matching lines @@
  public:
   enum Unit {
     kCounter,
     kByte,
   };
 
   Metric();
 
   static void InitOnce();
 
+  static void Cleanup();
+
   // Initialize and register a metric for an isolate.
   void Init(Isolate* isolate,
             const char* name,
             const char* description,
             Unit unit);
 
   // Initialize and register a metric for the VM.
   void Init(const char* name,
             const char* description,
             Unit unit);
 
   virtual ~Metric();
 
   void PrintJSON(JSONStream* stream);
 
+  // Returns a zone allocated string.
+  static char* ValueToString(int64_t value, Unit unit);
+
+  // Returns a zone allocated string.
+  char* ToString();
+
   int64_t value() const { return value_; }
   void set_value(int64_t value) { value_ = value; }
 
   void increment() { value_++; }
 
   Metric* next() const { return next_; }
   void set_next(Metric* next) {
     next_ = next;
   }
 
@@ skipping 69 matching lines @@
 
 class MetricIsolateCount : public Metric {
  protected:
   virtual int64_t Value() const;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_METRICS_H_