Fixed issue where initial 1KB zone buffer was not being accounted for when tracking thread zone me…

runtime/vm/zone.cc

Index: runtime/vm/zone.cc
diff --git a/runtime/vm/zone.cc b/runtime/vm/zone.cc
index b4c8e312cd1a4f08c6bb36d89361d174f99286a8..fc988a7ab230d946c00dba5b110b748a38418c0a 100644
--- a/runtime/vm/zone.cc
+++ b/runtime/vm/zone.cc
@@ -98,6 +98,10 @@ Zone::Zone()
       handles_(),
       previous_(NULL) {
   ASSERT(Utils::IsAligned(position_, kAlignment));
+  Thread* current = Thread::Current();
+  if (current != NULL) {
+    current->IncrementMemoryUsage(kInitialChunkSize);
+  }
 #ifdef DEBUG
   // Zap the entire initial buffer.
   memset(initial_buffer_.pointer(), kZapUninitializedByte,
@@ -110,6 +114,10 @@ Zone::~Zone() {
   if (FLAG_trace_zones) {
     DumpZoneSizes();
   }
+  Thread* current = Thread::Current();
+  if (current != NULL) {
+    current->DecrementMemoryUsage(kInitialChunkSize);
+  }
   DeleteAll();
 }