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

runtime/vm/zone.cc

Index: runtime/vm/zone.cc
diff --git a/runtime/vm/zone.cc b/runtime/vm/zone.cc
index 05e7eb75806ab7c1617d0f41e2d558236d39cdee..2925798efa2269462c21fdc5a9cc6d468086be89 100644
--- a/runtime/vm/zone.cc
+++ b/runtime/vm/zone.cc
@@ -92,6 +92,10 @@ 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,
@@ -104,6 +108,10 @@ Zone::~Zone() {
   if (FLAG_trace_zones) {
     DumpZoneSizes();
   }
+  Thread* current = Thread::Current();
+  if (current != NULL) {
+    current->DecrementMemoryUsage(kInitialChunkSize);
+  }
   DeleteAll();
 }