store SkAlphaType inside SkBitmap, on road to support unpremul

BUG=
R=bsalomon@google.com, scroggo@google.com

Review URL: https://codereview.chromium.org/25275004

git-svn-id: http://skia.googlecode.com/svn/trunk@11877 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/bench/BitmapScaleBench.cpp b/bench/BitmapScaleBench.cpp
index cc2a33a..ae3df71 100644
--- a/bench/BitmapScaleBench.cpp
+++ b/bench/BitmapScaleBench.cpp
@@ -57,14 +57,14 @@
     }
 
     virtual void onPreDraw() {
-        fInputBitmap.setConfig(SkBitmap::kARGB_8888_Config, fInputSize, fInputSize);
+        fInputBitmap.setConfig(SkBitmap::kARGB_8888_Config,
+                               fInputSize, fInputSize, 0, kOpaque_SkAlphaType);
         fInputBitmap.allocPixels();
         fInputBitmap.eraseColor(SK_ColorWHITE);
-        fInputBitmap.setIsOpaque(true);
 
-        fOutputBitmap.setConfig(SkBitmap::kARGB_8888_Config, fOutputSize, fOutputSize);
+        fOutputBitmap.setConfig(SkBitmap::kARGB_8888_Config,
+                                fOutputSize, fOutputSize, 0, kOpaque_SkAlphaType);
         fOutputBitmap.allocPixels();
-        fOutputBitmap.setIsOpaque(true);
 
         fMatrix.setScale( scale(), scale() );
     }