Add PDBs to .isolate files so that tests show stack traces.

content/content_browsertests.isolate

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 {
   'conditions': [
     ['OS=="android"', {
       'variables': {
         'isolate_dependency_tracked': [
           '<(PRODUCT_DIR)/content_shell/assets/content_shell.pak',
         ],
@@ skipping 67 matching lines @@
     ['OS=="win"', {
       'variables': {
         'isolate_dependency_tracked': [
           '<(PRODUCT_DIR)/content_shell.pak',
           '<(PRODUCT_DIR)/ffmpegsumo.dll',
           '<(PRODUCT_DIR)/osmesa.dll',
           '<(PRODUCT_DIR)/plugins/np_test_netscape_plugin.dll',
           '<(PRODUCT_DIR)/plugins/npapi_test_plugin.dll',
           '<(PRODUCT_DIR)/ppapi_tests.dll',
         ],
+        'isolate_dependency_untracked': [
+          '<(PRODUCT_DIR)/content_browsertests.exe.pdb',
+        ],
       },
     }],
   ],
   'includes': [
     '../third_party/icu/icu.isolate',
   ],
 }