Migrate handle scope fields to Thread.

runtime/vm/thread_test.cc

Index: runtime/vm/thread_test.cc
diff --git a/runtime/vm/thread_test.cc b/runtime/vm/thread_test.cc
index 0eccd6496a92fe6e481df963321fb1ce033a6582..f781783d8e43dd403a088228bc4248e126446c3d 100644
--- a/runtime/vm/thread_test.cc
+++ b/runtime/vm/thread_test.cc
@@ -117,9 +117,11 @@ class TaskWithZoneAllocation : public ThreadPool::Task {
   virtual void Run() {
     Thread::EnterIsolateAsHelper(isolate_);
     {
+      Thread* thread = Thread::Current();
       // Create a zone (which is also a stack resource) and exercise it a bit.
-      StackZone stack_zone(Thread::Current());
-      Zone* zone = Thread::Current()->zone();
+      StackZone stack_zone(thread);
+      HANDLESCOPE(thread);
+      Zone* zone = thread->zone();
       EXPECT_EQ(zone, stack_zone.GetZone());
       ZoneGrowableArray<bool>* a0 = new(zone) ZoneGrowableArray<bool>(zone, 1);
       GrowableArray<bool> a1(zone, 1);