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/SampleTextAlpha.cpp b/samplecode/SampleTextAlpha.cpp
index 83616f4..2732452 100644
--- a/samplecode/SampleTextAlpha.cpp
+++ b/samplecode/SampleTextAlpha.cpp
@@ -29,7 +29,7 @@
 #include "SkStream.h"
 
 static void check_for_nonwhite(const SkBitmap& bm, int alpha) {
-    if (bm.config() != SkBitmap::kRGB_565_Config) {
+    if (bm.colorType() != kRGB_565_SkColorType) {
         return;
     }