Initial prototype of vmstats support, based on Dart VM Stats draft design doc.

runtime/bin/vmstats.h

Index: runtime/bin/vmstats.h
===================================================================
--- runtime/bin/vmstats.h	(revision 0)
+++ runtime/bin/vmstats.h	(revision 0)
@@ -0,0 +1,37 @@
+// 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 BIN_VMSTATS_H_
+#define BIN_VMSTATS_H_
+
+#include "include/dart_api.h"
+
+/**
+ * A VM status callback. Status plug-ins implement and register this
+ * function using Dart_RegisterStatusPlugin. When Dart_GetVMStatus is
+ * called, each callback is invoked to provide the requested information,
+ * and the first one to do so "wins".
+ *
+ * Note: status requests execute outside of an isolate (which is why
+ * handles aren't used).
+ *
+ * \param request an optional string that defines REST-like parameters
+ *     to define what information is requested.
+ *
+ * \return Returns a valid JSON string, allocated from C heap. The caller
+ *     is responsible for releasing this string. NULL is returned if the
+ *     callback didn't handle that request.
+ */
+typedef char* (*Dart_VmStatusCallback)(const char* request);
+
+
+/**
+ * Register a VM status plug-in. The specified status type must not already
+ * have a registered plug-in.
+ *
+ * \return 0 if the plug-in was registered, or -1 if there is an error.
+ */
+DART_EXPORT int Dart_RegisterVmStatusPlugin(Dart_VmStatusCallback callback);
+
+#endif  // BIN_VMSTATS_H_