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..eb39501bc0db930332b1975252287f3673306a72 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 +92,19 @@ void ThreadRegistry::PrepareForGC() {
 }
 
 
+#ifndef PRODUCT
+void ThreadRegistry::PrintJSON(JSONStream* stream) const {
+  MonitorLocker ml(threads_lock());
+  JSONArray threads(stream);
+  Thread* current = active_list_;
+  while (current != NULL) {
+    threads.AddValue(current);
+    current = current->next_;
+  }
+}
+#endif
+
+
 void ThreadRegistry::AddToActiveListLocked(Thread* thread) {
   ASSERT(thread != NULL);
   ASSERT(threads_lock()->IsOwnedByCurrentThread());