StringViewize a bunch of things -- mostly LibGUI

Author: https://github.com/rburchell
Commit: 1024dfa81a
Pull-request: https://github.com/SerenityOS/serenity/pull/170
Reviewed-by: https://github.com/awesomekling

LibGUI/GCheckBox.cpp

@@ -27,7 +27,7 @@ GCheckBox::GCheckBox(GWidget* parent)
 {
 }
 
-GCheckBox::GCheckBox(const String& text, GWidget* parent)
+GCheckBox::GCheckBox(const StringView& text, GWidget* parent)
     : GAbstractButton(text, parent)
 {
 }