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..1cde2e50c4b08d6b5c6a9bc8d229b18357bd9a7b 100644
--- a/runtime/vm/thread.cc
+++ b/runtime/vm/thread.cc
@@ -38,6 +38,8 @@ Thread::~Thread() {
     delete compiler_stats_;
     compiler_stats_ = NULL;
   }
+  // All zone allocated memory should be free by this point.
+  ASSERT(current_thread_memory_ == 0);
   // There should be no top api scopes at this point.
   ASSERT(api_top_scope() == NULL);
   // Delete the resusable api scope if there is one.
@@ -74,6 +76,8 @@ 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 +217,7 @@ 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_);

[Cutch, 2017/01/03 20:58:54]

The value of 'thread_memory_high_watermark_' seems to get reset whenever a
thread enters an isolate. So this can't be the memory high watermark.

[bkonyi, 2017/01/04 00:31:54]

Is this still a concern given your previous comments in isolate.cc?

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