Support use of external strings as inputs to LoadCodeUnitsInstr.

runtime/vm/vm_sources.gypi

 # Copyright (c) 2013, 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.
 
 # This file contains all sources (vm and tests) for the dart virtual machine.
 # Unit test files need to have a '_test' suffix appended to the name.
 {
   'sources': [
     'allocation.cc',
     'allocation.h',
@@ skipping 321 matching lines @@
     'raw_object.h',
     'raw_object_snapshot.cc',
     'regexp.cc',
     'regexp.h',
     'regexp_assembler.cc',
     'regexp_assembler.h',
     'regexp_ast.cc',
     'regexp_ast.h',
     'regexp_parser.cc',
     'regexp_parser.h',
+    'regexp_test.cc',
     'report.cc',
     'report.h',
     'report_test.cc',
     'resolver.cc',
     'resolver.h',
     'resolver_test.cc',
     'reusable_handles.h',
     'ring_buffer.h',
     'ring_buffer_test.cc',
     'runtime_entry.h',
@@ skipping 112 matching lines @@
     'vtune.h',
     'weak_code.cc',
     'weak_code.h',
     'weak_table.cc',
     'weak_table.h',
     'zone.cc',
     'zone.h',
     'zone_test.cc',
   ],
 }