Added conversion from thread id to intptr that fixes breaking build.

runtime/vm/thread.cc

Index: runtime/vm/thread.cc
diff --git a/runtime/vm/thread.cc b/runtime/vm/thread.cc
index c09a9f02593c1a6907ba2468cc90bb15dccd5026..c91500be28d31e3e72ff043ba8e76a5a33fb4f88 100644
--- a/runtime/vm/thread.cc
+++ b/runtime/vm/thread.cc
@@ -211,7 +211,8 @@ void Thread::InitVMConstants() {
 void Thread::PrintJSON(JSONStream* stream) const {
   JSONObject jsobj(stream);
   jsobj.AddProperty("type", "_Thread");
-  jsobj.AddPropertyF("id", "threads/%" Pd64 "", os_thread()->trace_id());
+  jsobj.AddPropertyF("id", "threads/%" Pd64 "",
+                     ThreadIdToIntPtr(os_thread()->trace_id()));

[zra, 2016/12/12 18:20:53]

Sorry, I should have noticed that it looks like this needs to be
OSThread::ThreadIdToIntPtr().

   Zone* zone = zone_;
   {
     JSONArray zone_info_array(&jsobj, "zones");