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/SkCanvasWidget.cpp b/debugger/QT/SkCanvasWidget.cpp
index 3c239d0..73de8c2 100644
--- a/debugger/QT/SkCanvasWidget.cpp
+++ b/debugger/QT/SkCanvasWidget.cpp
@@ -129,6 +129,13 @@
 #endif
 }
 
+#if SK_SUPPORT_GPU
+void SkCanvasWidget::setGLSampleCount(int sampleCount)
+{
+    fGLWidget.setSampleCount(sampleCount);
+}
+#endif
+
 void SkCanvasWidget::zoom(float scale, int px, int py) {
     fUserMatrix.postScale(scale, scale, px, py);
     emit scaleFactorChanged(fUserMatrix.getScaleX());