Added isolate + thread high watermark tracking to Observatory

runtime/vm/thread.cc

Index: runtime/vm/thread.cc
diff --git a/runtime/vm/thread.cc b/runtime/vm/thread.cc
index 1b3428eaa62eba6a88e01859b9b294528db1cce3..012eb14006c195c3139683ba815ad7ed00b6f4da 100644
--- a/runtime/vm/thread.cc
+++ b/runtime/vm/thread.cc
@@ -74,6 +74,8 @@ Thread::Thread(Isolate* isolate)
       os_thread_(NULL),
       thread_lock_(new Monitor()),
       zone_(NULL),
+      current_thread_memory_(0),
+      thread_memory_high_watermark_(0),
       api_reusable_scope_(NULL),
       api_top_scope_(NULL),
       top_resource_(NULL),
@@ -213,6 +215,7 @@ void Thread::PrintJSON(JSONStream* stream) const {
   jsobj.AddPropertyF("id", "threads/%" Pd "",
                      OSThread::ThreadIdToIntPtr(os_thread()->trace_id()));
   jsobj.AddProperty("kind", TaskKindToCString(task_kind()));
+  jsobj.AddProperty("threadMemoryHighWatermark", thread_memory_high_watermark_);
   Zone* zone = zone_;
   {
     JSONArray zone_info_array(&jsobj, "zones");