Added ctrl-\ command that dumps isolate stacks to dart binary.

runtime/bin/vmstats_impl.h

Index: runtime/bin/vmstats_impl.h
===================================================================
--- runtime/bin/vmstats_impl.h	(revision 20895)
+++ runtime/bin/vmstats_impl.h	(working copy)
@@ -17,6 +17,8 @@
 
 class VmStats {
  public:
+  static void Initialize();
+
   static void Start(int port, const char* root_dir);
   static void Stop();
 
@@ -24,9 +26,13 @@
   static void AddIsolate(IsolateData* isolate_data, Dart_Isolate isolate);
   static void RemoveIsolate(IsolateData* isolate_data);
 
+  // Print stack traces of current isolates to stdout.
+  static void DumpStack();
+
  private:
   VmStats() : root_directory_(NULL), running_(false), bind_address_(0) {}
 
+  static void StartServer(int port, const char* root_dir);
   static void WebServer(uword bind_address);
   static void Shutdown();