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/GAbstractButton.cpp

@@ -6,7 +6,7 @@ GAbstractButton::GAbstractButton(GWidget* parent)
 {
 }
 
-GAbstractButton::GAbstractButton(const String& text, GWidget* parent)
+GAbstractButton::GAbstractButton(const StringView& text, GWidget* parent)
     : GWidget(parent)
     , m_text(text)
 {
@@ -16,7 +16,7 @@ GAbstractButton::~GAbstractButton()
 {
 }
 
-void GAbstractButton::set_text(const String& text)
+void GAbstractButton::set_text(const StringView& text)
 {
     if (m_text == text)
         return;