Add missing Dart_ExitScope calls in some of the VM unit tests.

runtime/vm/dart_api_impl_test.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "bin/builtin.h"
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 #include "include/dart_tools_api.h"
 #include "platform/assert.h"
@@ skipping 2801 matching lines @@
 
 UNIT_TEST_CASE(WeakPersistentHandlesCallbackShutdown) {
   TestCase::CreateTestIsolate();
   Dart_EnterScope();
   Dart_Handle ref = Dart_True();
   int peer = 1234;
   Dart_NewWeakPersistentHandle(ref,
                                &peer,
                                0,
                                WeakPersistentHandlePeerFinalizer);
+  Dart_ExitScope();
   Dart_ShutdownIsolate();
   EXPECT(peer == 42);
 }
 
 
 TEST_CASE(WeakPersistentHandleExternalAllocationSize) {
   Heap* heap = Isolate::Current()->heap();
   EXPECT(heap->ExternalInWords(Heap::kNew) == 0);
   EXPECT(heap->ExternalInWords(Heap::kOld) == 0);
   Dart_WeakPersistentHandle weak1 = NULL;
@@ skipping 6930 matching lines @@
   EXPECT_SUBSTRING("\"function\":\"::_main\"", buffer);
 
   // Heartbeat test for new events.
   EXPECT_SUBSTRING("\"name\":\"TestVMDuration2\"", buffer);
   EXPECT_SUBSTRING("\"function\":\"::_bar\"", buffer);
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart