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/tests/ARGBImageEncoderTest.cpp b/tests/ARGBImageEncoderTest.cpp
index 9f68a0a..bffcaa4 100644
--- a/tests/ARGBImageEncoderTest.cpp
+++ b/tests/ARGBImageEncoderTest.cpp
@@ -48,7 +48,7 @@
         {
             bitmap.setConfig(configs[configIndex], kWidth, kHeight);
             REPORTER_ASSERT(reporter, bitmap.allocPixels());
-            bitmap.setIsOpaque(true);
+            bitmap.setAlphaType(kOpaque_SkAlphaType);
             bitmap.eraseColor(SK_ColorBLUE);
             // Change rows [0,1] from blue to [red,green].
             SkCanvas canvas(bitmap);