use SkColorType instead of SkBitmap::Config in samplecode

BUG=skia:
R=reed@google.com

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/169063002

git-svn-id: http://skia.googlecode.com/svn/trunk@13473 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/samplecode/SampleRotateCircles.cpp b/samplecode/SampleRotateCircles.cpp
index 537f424..f9b32ea 100644
--- a/samplecode/SampleRotateCircles.cpp
+++ b/samplecode/SampleRotateCircles.cpp
@@ -108,8 +108,7 @@
         int h = w;
 
         SkBitmap bm;
-        bm.setConfig(SkBitmap::kARGB_8888_Config, w, h);
-        bm.allocPixels();
+        bm.allocN32Pixels(w, h);
         bm.eraseColor(0);
 
         SkAutoLockPixels alp(bm);