Support MSAA in the picture debugger

Add radio buttons for setting the GL sample count to 0 ("off"), 4 or
16.

Change the default mode of the GL widget to MSAA4. Previous behavior
corresponded to "off".

BUG=1459
R=robertphillips@google.com

Author: kkinnunen@nvidia.com

Review URL: https://chromiumcodereview.appspot.com/21752002

git-svn-id: http://skia.googlecode.com/svn/trunk@10509 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/debugger/QT/SkDebuggerGUI.h b/debugger/QT/SkDebuggerGUI.h
index 3122638..13ec181 100644
--- a/debugger/QT/SkDebuggerGUI.h
+++ b/debugger/QT/SkDebuggerGUI.h
@@ -114,9 +114,9 @@
 
 #if SK_SUPPORT_GPU
     /**
-        Toggles the visibility of the GL canvas widget.
+        Updates the visibility of the GL canvas widget and sample count of the GL surface.
      */
-    void actionGLWidget(bool isToggled);
+    void actionGLWidget();
 #endif
 
     /**