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

runtime/vm/thread_registry.h

Index: runtime/vm/thread_registry.h
diff --git a/runtime/vm/thread_registry.h b/runtime/vm/thread_registry.h
index eb2d327f64ebac1a7ce8828ea3eb341fcba6baaa..2f8da529f55e5fa1779cea065e94c8ba5e3eb5e1 100644
--- a/runtime/vm/thread_registry.h
+++ b/runtime/vm/thread_registry.h
@@ -12,6 +12,11 @@
 #include "vm/stack_frame.h"
 #include "vm/thread.h"
 
+#ifndef PRODUCT
+class JSONStream;
+class JSONArray;
+#endif
+
 namespace dart {
 
 // Unordered collection of threads relating to a particular isolate.
@@ -28,6 +33,10 @@ class ThreadRegistry {
   void PrepareForGC();
   Thread* mutator_thread() const { return mutator_thread_; }
 
+#ifndef PRODUCT
+  void PrintJSON(JSONStream* stream) const;
+#endif
+
  private:
   Thread* active_list() const { return active_list_; }
   Monitor* threads_lock() const { return threads_lock_; }
@@ -39,6 +48,10 @@ class ThreadRegistry {
   Thread* GetFromFreelistLocked(Isolate* isolate);
   void ReturnToFreelistLocked(Thread* thread);
 
+#ifndef PRODUCT
+  void PrintJSONHelper(JSONArray* array, Thread* thread) const;
+#endif
+
   // This monitor protects the threads list for an isolate, it is used whenever
   // we need to iterate over threads (both active and free) in an isolate.
   Monitor* threads_lock_;