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/SampleUnpremul.cpp b/samplecode/SampleUnpremul.cpp
index 58d8ec2..f2f60cc 100644
--- a/samplecode/SampleUnpremul.cpp
+++ b/samplecode/SampleUnpremul.cpp
@@ -125,10 +125,7 @@
             // Copy it to a bitmap which can be drawn, converting
             // to premultiplied:
             SkBitmap bm;
-            bm.setConfig(SkBitmap::kARGB_8888_Config, fBitmap.width(),
-                         fBitmap.height());
-            SkASSERT(fBitmap.config() == SkBitmap::kARGB_8888_Config);
-            if (!bm.allocPixels()) {
+            if (!bm.allocN32Pixels(fBitmap.width(), fBitmap.height())) {
                 SkString errMsg("allocPixels failed");
                 canvas->drawText(errMsg.c_str(), errMsg.size(), 0, height, paint);
                 return;