Update the error message in the Files app via Downloads panel.

chrome/browser/chromeos/file_manager/open_util.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/chromeos/file_manager/open_util.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 124 matching lines @@
       profile,
       path,
       base::Bind(&OpenFileWithMimeType, profile, path, url, callback));
 }
 
 // Called when execution of ContinueOpenItem() is completed.
 void OnContinueOpenItemCompleted(Profile* profile,
                                  const base::FilePath& file_path,
                                  bool result) {
   if (!result) {
-    ShowWarningMessageBox(
-        profile, file_path, IDS_FILE_BROWSER_ERROR_VIEWING_FILE);
+    int message;
+    if (file_path.Extension() == ".dmg")

[kinaba, 2014/09/11 08:50:41]

FILE_PATH_LITERAL(".dmg")

base::FilePath holds UTF-16 chars on Windows and UTF-8 on others.
FILE_PATH_LITERAL is a macro for absorbing the type difference.

Although the current code runs only on Chrome OS, we still want
to keep the code as portable as possible.

Same applies for ".exe" below.

[iseki, 2014/09/11 09:18:58]

Done.

+      message = IDS_FILE_BROWSER_ERROR_VIEWING_FILE_FOR_DMG;
+    else if (file_path.Extension() == ".exe")

[kinaba, 2014/09/11 08:50:41]

Would you mind checking ".msi" and returning the same message as ".exe"?
Actually I've silently tweaked it a bit for JS code last week. :)
https://codereview.chromium.org/541593003/

[iseki, 2014/09/11 09:18:58]

Done.

+      message = IDS_FILE_BROWSER_ERROR_VIEWING_FILE_FOR_EXECUTABLE;
+    else
+      message = IDS_FILE_BROWSER_ERROR_VIEWING_FILE;
+    ShowWarningMessageBox(profile, file_path, message);
   }
 }
 
 // Used to implement OpenItem().
 void ContinueOpenItem(Profile* profile,
                       const base::FilePath& file_path,
                       const GURL& url,
                       base::File::Error error) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
@@ skipping 67 matching lines @@
   GURL url;
   if (!ConvertPath(profile, file_path, &converted_path, &url))
     return;
 
   // This action changes the selection so we do not reuse existing tabs.
   OpenFileManagerWithInternalActionId(profile, url, "select");
 }
 
 }  // namespace util
 }  // namespace file_manager