Created methods to surface zone memory information for each isolate and thread in JSON.

runtime/vm/thread_registry.cc

Index: runtime/vm/thread_registry.cc
diff --git a/runtime/vm/thread_registry.cc b/runtime/vm/thread_registry.cc
index c660843c1eac3bd892de539293114b2dae1632c6..5f62350692da94f334c07e9d2bfea0f4d65f51b1 100644
--- a/runtime/vm/thread_registry.cc
+++ b/runtime/vm/thread_registry.cc
@@ -5,6 +5,7 @@
 #include "vm/thread_registry.h"
 
 #include "vm/isolate.h"
+#include "vm/json_stream.h"
 #include "vm/lockers.h"
 
 namespace dart {
@@ -91,6 +92,30 @@ void ThreadRegistry::PrepareForGC() {
 }
 
 
+#ifndef RELEASE
+void ThreadRegistry::PrintToJSONObjectLocked(JSONObject* obj) {
+  MonitorLocker ml(threads_lock());
+  {
+    JSONArray active_thread_array(obj, "active_threads");
+    PrintToJSONObjectHelper(&active_thread_array, active_list_);
+  }
+  {
+    JSONArray free_thread_array(obj, "free_threads");
+    PrintToJSONObjectHelper(&free_thread_array, free_list_);
+  }
+}
+
+
+void ThreadRegistry::PrintToJSONObjectHelper(JSONArray* arr, Thread* thread) {
+  while (thread != NULL) {
+    JSONObject thread_obj(arr);
+    thread->PrintToJSONObject(&thread_obj);
+    thread = thread->next_;
+  }
+}
+#endif
+
+
 void ThreadRegistry::AddToActiveListLocked(Thread* thread) {
   ASSERT(thread != NULL);
   ASSERT(threads_lock()->IsOwnedByCurrentThread());