EN, mf, DO YOU SPEAK IT?

chrome/tools/mac_helpers/infoplist_strings_util.mm

 // 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.
 
 // Helper tool that is built and run during a build to pull strings from
 // the GRD files and generate the InfoPlist.strings files needed for
 // Mac OS X app bundles.
 
 #import <Foundation/Foundation.h>
 
@@ skipping 248 matching lines @@
     // put them final runtime encoding.
     NSData* strings_file_contents_utf8 =
         [strings_file_contents_string dataUsingEncoding:NSUTF8StringEncoding];
 
     if ([strings_file_contents_utf8 length] == 0) {
       fprintf(stderr, "ERROR: failed to get the utf8 encoding of the strings "
               "file for language: %s\n", cur_lang);
       exit(1);
     }
 
+    // For Cocoa to find the locale at runtime, it needs to use '_' instead of
+    // '-' (http://crbug.com/20441).  Also, 'en-US' should be represented
+    // simply as 'en' (http://crbug.com/19165, http://crbug.com/25578).
+    NSString* cur_lang_ns = [NSString stringWithUTF8String:cur_lang];
+    if ([cur_lang_ns isEqualToString:@"en-US"]) {
+      cur_lang_ns = @"en";
+    }
+    cur_lang_ns = [cur_lang_ns stringByReplacingOccurrencesOfString:@"-"
+                                                         withString:@"_"];
     // Make sure the lproj we write to exists
-    NSString *lproj_name = [NSString stringWithFormat:@"%s.lproj", cur_lang];
-    // For Cocoa to find the locale at runtime, it needs to use '_' instead of
-    // '-'.  (http://crbug.com/20441)
-    lproj_name = [lproj_name stringByReplacingOccurrencesOfString:@"-"
-                                                       withString:@"_"];
+    NSString *lproj_name = [NSString stringWithFormat:@"%@.lproj", cur_lang_ns];
     NSString *output_path =
         [[NSString stringWithUTF8String:output_dir]
          stringByAppendingPathComponent:lproj_name];
     NSError* error = nil;
     if (![fm fileExistsAtPath:output_path] &&
         ![fm createDirectoryAtPath:output_path
         withIntermediateDirectories:YES
                         attributes:nil
                              error:&error]) {
       fprintf(stderr, "ERROR: '%s' didn't exist or we failed to create it\n",
               [output_path UTF8String]);
       exit(1);
     }
 
     // Write out the file
     output_path =
         [output_path stringByAppendingPathComponent:@"InfoPlist.strings"];
     if (![strings_file_contents_utf8 writeToFile:output_path
                                       atomically:YES]) {
       fprintf(stderr, "ERROR: Failed to write out '%s'\n",
               [output_path UTF8String]);
       exit(1);
     }
   }
   return 0;
 }