The newer version seems to have moved where the nib lives.

breakpad/breakpad.gyp

 # Copyright (c) 2009 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.
 
 {
   'includes': [
     '../build/common.gypi',
   ],
   'conditions': [
     [ 'OS=="mac"', {
@@ skipping 53 matching lines @@
           'type': 'executable',
           'mac_bundle': 1,
           'sources': [
             'src/common/mac/HTTPMultipartUpload.m',
             'src/client/mac/sender/crash_report_sender.m',
             'src/common/mac/GTMLogger.m',
           ],
           'mac_bundle_resources': [
             'src/client/mac/sender/English.lproj/Localizable.strings',
             'src/client/mac/sender/crash_report_sender.icns',
-            'src/client/mac/sender/English.lproj/Breakpad.nib',
+            'src/client/mac/sender/Breakpad.nib',
             'src/client/mac/sender/crash_report_sender-Info.plist',
           ],
           'mac_bundle_resources!': [
              'src/client/mac/sender/crash_report_sender-Info.plist',
           ],
           'xcode_settings': {
              'INFOPLIST_FILE': 'src/client/mac/sender/crash_report_sender-Info.plist',
           },
           'link_settings': {
             'libraries': [
@@ skipping 115 matching lines @@
           'direct_dependent_settings': {
             'include_dirs': [
               'src',
             ],
           },
         },
       ],
     }],
   ],
 }