Fix CefCommandLine character case requirements (fixes issue #1872)

Switch names will now be converted to lowercase ASCII on all platforms.
Switch values will retain the original case and UTF8 encoding.

include/cef_command_line.h

@@ -49,8 +49,9 @@
 // optionally have a value specified using the '=' delimiter (e.g.
 // "-switch=value"). An argument of "--" will terminate switch parsing with all
 // subsequent tokens, regardless of prefix, being interpreted as non-switch
-// arguments. Switch names are considered case-insensitive. This class can be
-// used before CefInitialize() is called.
+// arguments. Switch names should be lowercase ASCII and will be converted to
+// such if necessary. Switch values will retain the original case and UTF8
+// encoding. This class can be used before CefInitialize() is called.
 ///
 /*--cef(source=library,no_debugct_check)--*/
 class CefCommandLine : public virtual CefBaseRefCounted {