Add utility function to determine if a locale is valid syntax; this will...

chrome/common/extensions/extension_l10n_util.h

Index: chrome/common/extensions/extension_l10n_util.h
===================================================================
--- chrome/common/extensions/extension_l10n_util.h	(revision 67716)
+++ chrome/common/extensions/extension_l10n_util.h	(working copy)
@@ -86,6 +86,14 @@
                      std::set<std::string>* locales,
                      std::string* error);
 
+// Checks if a string is plausibly a syntactically-valid locale string,
+// for cases where we want the valid input to be a locale string such as
+// 'en', 'pt-BR', 'fil', and 'zh-Hans-CN', but we don't want to limit it
+// to locales that Chrome actually knows about, so 'xx-YY' should be
+// accepted, but 'z', 'German', 'en-$1', or 'abcd-1234' should not.
+// Case-insensitive. Based on RFC 5646.
+bool IsValidLocaleSyntax(const std::string& locale);
+
 // Loads messages file for default locale, and application locales (application
 // locales doesn't have to exist). Application locale is current locale and its
 // parents.