Added tracking of memory usage within ApiNativeScopes. Usage to be displayed within Observatory.

runtime/vm/zone_test.cc

Index: runtime/vm/zone_test.cc
diff --git a/runtime/vm/zone_test.cc b/runtime/vm/zone_test.cc
index ba0a25b188c922647cdcb3ba0896a6849aecaa13..21b50c0076cd2c4efc69e2011678f226092c406c 100644
--- a/runtime/vm/zone_test.cc
+++ b/runtime/vm/zone_test.cc
@@ -228,4 +228,20 @@ UNIT_TEST_CASE(PrintZoneMemoryInfoToJSON) {
 }
 #endif
 
+
+UNIT_TEST_CASE(NativeScopeZoneAllocation) {
+  ASSERT(ApiNativeScope::Current() == NULL);
+  ASSERT(Thread::Current() == NULL);
+  EXPECT_EQ(0, ApiNativeScope::current_memory_usage());
+  {
+    ApiNativeScope scope;
+    EXPECT_EQ(scope.zone()->CapacityInBytes(),
+              ApiNativeScope::current_memory_usage());
+    (void)Dart_ScopeAllocate(2048);
+    EXPECT_EQ(scope.zone()->CapacityInBytes(),
+              ApiNativeScope::current_memory_usage());
+  }
+  EXPECT_EQ(0, ApiNativeScope::current_memory_usage());
+}
+
 }  // namespace dart