Bug 1394311: Use lowercase consistently for looking up the language group. r=manishearth

This should be the only callee affected, given
gfxPlatformFontList::GetFontPrefLangFor already uses case-insensitive string
comparison.

This makes it also consistent with the rest of the functions in the file, which
lowercase their inputs as well.

MozReview-Commit-ID: 4fNUBdpayHL

--HG--
extra : rebase_source : d669f5da2a1ed06f6348fc6b86eb379b514ddcf3

intl/locale/nsLanguageAtomService.cpp

@@ -101,6 +101,7 @@ nsLanguageAtomService::GetUncachedLanguageGroup(nsIAtom* aLanguage) const
 {
   nsAutoCString langStr;
   aLanguage->ToUTF8String(langStr);
+  ToLowerCase(langStr);
 
   nsAutoCString langGroupStr;
   nsresult res =