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/GFilePicker.cpp

@@ -12,7 +12,7 @@
 #include <LibGUI/GToolBar.h>
 #include <SharedGraphics/PNGLoader.h>
 
-GFilePicker::GFilePicker(const String& path, CObject* parent)
+GFilePicker::GFilePicker(const StringView& path, CObject* parent)
     : GDialog(parent)
     , m_model(GDirectoryModel::create())
 {