hide SkBitmap::setConfig

tools/skpdiff/SkDifferentPixelsMetric_cpu.cpp

Index: tools/skpdiff/SkDifferentPixelsMetric_cpu.cpp
diff --git a/tools/skpdiff/SkDifferentPixelsMetric_cpu.cpp b/tools/skpdiff/SkDifferentPixelsMetric_cpu.cpp
index 27c7a135d7d094ee757de452c44e4c727330e85a..768bfc7d21aea34811db02baf291ba2e39d6f68d 100644
--- a/tools/skpdiff/SkDifferentPixelsMetric_cpu.cpp
+++ b/tools/skpdiff/SkDifferentPixelsMetric_cpu.cpp
@@ -30,9 +30,7 @@ bool SkDifferentPixelsMetric::diff(SkBitmap* baseline, SkBitmap* test, bool comp
 
     // Prepare the POI alpha mask if needed
     if (computeMask) {
-        result->poiAlphaMask.setConfig(SkBitmap::kA8_Config, width, height);
-        result->poiAlphaMask.allocPixels();
-        result->poiAlphaMask.lockPixels();
+        result->poiAlphaMask.allocPixels(SkImageInfo::MakeA8(width, height));
         result->poiAlphaMask.eraseARGB(SK_AlphaOPAQUE, 0, 0, 0);
     }