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/GMessageBox.cpp

@@ -4,13 +4,13 @@
 #include <LibGUI/GButton.h>
 #include <stdio.h>
 
-void GMessageBox::show(const String& text, const String& title, Type type, CObject* parent)
+void GMessageBox::show(const StringView& text, const StringView& title, Type type, CObject* parent)
 {
     GMessageBox box(text, title, type, parent);
     box.exec();
 }
 
-GMessageBox::GMessageBox(const String& text, const String& title, Type type, CObject* parent)
+GMessageBox::GMessageBox(const StringView& text, const StringView& title, Type type, CObject* parent)
     : GDialog(parent)
     , m_text(text)
     , m_type(type)