stop using SkBitmap::Config

R=scroggo@google.com

Author: reed@chromium.org

Review URL: https://codereview.chromium.org/338493005
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index 11a79db..72b0737 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -1376,7 +1376,7 @@
     // the rest from the SkPaint.
     GrPaint grPaint;
     grPaint.addColorEffect(effect);
-    bool alphaOnly = !(SkBitmap::kA8_Config == bitmap.config());
+    bool alphaOnly = !(kAlpha_8_SkColorType == bitmap.colorType());
     GrColor grColor = (alphaOnly) ? SkColor2GrColorJustAlpha(paint.getColor()) :
                                     SkColor2GrColor(paint.getColor());
     SkPaint2GrPaintNoShader(this->context(), paint, grColor, false, &grPaint);