Prevent crashes in mime_util_xdg.

base/nix/mime_util_xdg.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 "base/nix/mime_util_xdg.h"
 
 #include <cstdlib>
 #include <list>
 #include <map>
 #include <vector>
@@ skipping 570 matching lines @@
   for (size_t i = 0; i < kDefaultThemeNum; i++)
     delete default_themes_[i];
 }
 
 }  // namespace
 
 namespace base {
 namespace nix {
 
 std::string GetFileMimeType(const FilePath& filepath) {
+  if (filepath.empty())

[Lei Zhang, 2012/08/22 05:59:10]

Curious, who is calling GetFileMimeType with an empty filepath?
IconManager::LoadIcon() ?

[benjhayden, 2012/08/22 14:24:14]

Yes, LoadIcon() doesn't early-return for empty paths, iirc.
No, nothing is currently calling LoadIcon() with an empty path, afaik. We're
currently refactoring the downloads system, and in a few of my recent refactors,
I had bugs where I was calling LoadIcon() with an empty path. I fixed the bugs,
but until I get around to writing a lot more tests, it could easily come back,
and I'd rather display a blank icon than crash.

+    return std::string();
   base::ThreadRestrictions::AssertIOAllowed();
   base::AutoLock scoped_lock(g_mime_util_xdg_lock.Get());
   return xdg_mime_get_mime_type_from_file_name(filepath.value().c_str());
 }
 
 std::string GetDataMimeType(const std::string& data) {
   base::ThreadRestrictions::AssertIOAllowed();
   base::AutoLock scoped_lock(g_mime_util_xdg_lock.Get());
   return xdg_mime_get_mime_type_for_data(data.data(), data.length(), NULL);
 }
@@ skipping 17 matching lines @@
   g_free(gtk_theme_name);
 }
 #endif
 
 FilePath GetMimeIcon(const std::string& mime_type, size_t size) {
   base::ThreadRestrictions::AssertIOAllowed();
   std::vector<std::string> icon_names;
   std::string icon_name;
   FilePath icon_file;
 
-  {
+  if (!mime_type.empty()) {
     base::AutoLock scoped_lock(g_mime_util_xdg_lock.Get());
     const char *icon = xdg_mime_get_icon(mime_type.c_str());
     icon_name = std::string(icon ? icon : "");
   }
 
   if (icon_name.length())
     icon_names.push_back(icon_name);
 
   // For text/plain, try text-plain.
   icon_name = mime_type;
@@ skipping 28 matching lines @@
       icon_file = LookupIconInDefaultTheme(icon_names[i], size);
       if (!icon_file.empty())
         return icon_file;
     }
   }
   return FilePath();
 }
 
 }  // namespace nix
 }  // namespace base