Add Metrics for heap high water marks

runtime/vm/metrics.cc

 // 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.
 
 #include "vm/metrics.h"
 
 #include "vm/isolate.h"
 #include "vm/json_stream.h"
 #include "vm/native_entry.h"
 #include "vm/runtime_entry.h"
@@ skipping 289 matching lines @@
     OS::Print("Printing metrics for VM\n");
     Metric* current = Metric::vm_head();
     while (current != NULL) {
       OS::Print("%s\n", current->ToString());
       current = current->next();
     }
     OS::Print("\n");
   }
 }
 
+
+MaxMetric::MaxMetric()
+    : Metric() {
+  set_value(kMinInt64);
+}
+
+
+void MaxMetric::SetValue(int64_t new_value) {
+  if (new_value > value()) {
+    set_value(new_value);
+  }
+}
+
+
+MinMetric::MinMetric()
+    : Metric() {
+  set_value(kMaxInt64);
+}
+
+
+void MinMetric::SetValue(int64_t new_value) {
+  if (new_value < value()) {
+    set_value(new_value);
+  }
+}
+
 }  // namespace dart