Remove corelib/corelib_strong and migrate last two remaining tests.

PRESUBMIT.py

 # 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.
 
 """Top-level presubmit script for Dart.
 
 See http://dev.chromium.org/developers/how-tos/depottools/presubmit-scripts
 for more details about the presubmit API built into gcl.
 """
 
@@ skipping 80 matching lines @@
         'Fix these issues with:\n'
         '%s -w \\\n%s' % (prebuilt_dartfmt, ' \\\n'.join(unformatted_files)))]
 
   return []
 
 def _CheckNewTests(input_api, output_api):
   testsDirectories = [
       #    Dart 1 tests                DDC tests
       # =================       ==========================
       ("tests/language/",       "tests/language_2/"),
-      ("tests/corelib/",        "tests/corelib_2/"),
       ("tests/lib/",            "tests/lib_2/"),
       ("tests/html/",           "tests/lib_2/html/"),
   ]
 
   result = []
   # Tuples of (new Dart 1 test path, expected DDC test path)
   dart1TestsAdded = []
   # Tuples of (original Dart test path, expected DDC test path)
   ddcTestsExists = []
   for f in input_api.AffectedFiles():
@@ skipping 52 matching lines @@
   return result
 
 def CheckChangeOnCommit(input_api, output_api):
   return (_CheckBuildStatus(input_api, output_api) +
           _CheckNewTests(input_api, output_api) +
           _CheckDartFormat(input_api, output_api))
 
 def CheckChangeOnUpload(input_api, output_api):
   return (_CheckNewTests(input_api, output_api) +
           _CheckDartFormat(input_api, output_api))