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/SampleWritePixels.cpp b/samplecode/SampleWritePixels.cpp
index 04f3484..f7829ea 100644
--- a/samplecode/SampleWritePixels.cpp
+++ b/samplecode/SampleWritePixels.cpp
@@ -19,8 +19,7 @@
 static void create_bitmap(SkBitmap* bitmap) {
     const int W = 100;
     const int H = 100;
-    bitmap->setConfig(SkBitmap::kARGB_8888_Config, W, H);
-    bitmap->allocPixels();
+    bitmap->allocN32Pixels(W, H);
 
     SkCanvas canvas(*bitmap);
     canvas.drawColor(SK_ColorRED);