Reimplemented zone memory tracking to avoid race conditions that were causing crashes in the previo…

runtime/vm/json_stream.cc

Index: runtime/vm/json_stream.cc
diff --git a/runtime/vm/json_stream.cc b/runtime/vm/json_stream.cc
index 0f041174a8d574d2e06fb2f0adaf0bdb012bd097..d95345b4953c184401adf3e477710531c5b33f80 100644
--- a/runtime/vm/json_stream.cc
+++ b/runtime/vm/json_stream.cc
@@ -562,12 +562,6 @@ void JSONStream::PrintValue(Thread* thread) {
 }
 
 
-void JSONStream::PrintValue(Zone* zone) {
-  PrintCommaIfNeeded();
-  zone->PrintJSON(this);
-}
-
-
 void JSONStream::PrintValue(const TimelineEvent* timeline_event) {
   PrintCommaIfNeeded();
   timeline_event->PrintJSON(this);
@@ -703,12 +697,6 @@ void JSONStream::PrintProperty(const char* name, Thread* thread) {
 }
 
 
-void JSONStream::PrintProperty(const char* name, Zone* zone) {
-  PrintPropertyName(name);
-  PrintValue(zone);
-}
-
-
 void JSONStream::PrintProperty(const char* name,
                                const TimelineEvent* timeline_event) {
   PrintPropertyName(name);