Begins work on ARM64, first assembler test.

runtime/vm/custom_isolate_test.cc

 // Copyright (c) 2011, 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.
 
+// TODO(zra): Remove when tests are ready to enable.
+#include "platform/globals.h"
+#if !defined(TARGET_ARCH_ARM64)
+
 #include "include/dart_api.h"
 #include "include/dart_native_api.h"
 
 #include "vm/unit_test.h"
 
 // Custom Isolate Test.
 //
 // This mid-size test uses the Dart Embedding Api to create a custom
 // isolate abstraction.  Instead of having a dedicated thread for each
 // isolate, as is the case normally, this implementation shares a
@@ skipping 328 matching lines @@
     event = event_queue->Get();
   }
   OS::Print("-- Finished event loop --\n");
   EXPECT_STREQ("Received: 43", saved_echo);
   free(const_cast<char*>(saved_echo));
 
   delete event_queue;
 }
 
 }  // namespace dart
+
+#endif  // !defined(TARGET_ARCH_ARM64)