store SkAlphaType inside SkBitmap, on road to support unpremul

tests/ShaderOpacityTest.cpp

Index: tests/ShaderOpacityTest.cpp
diff --git a/tests/ShaderOpacityTest.cpp b/tests/ShaderOpacityTest.cpp
index 0af25d1ec21e9e09e7c79c49a248f1bce2357f53..c3dc888ba35098632b2fd7ab3669ea08fe62142f 100644
--- a/tests/ShaderOpacityTest.cpp
+++ b/tests/ShaderOpacityTest.cpp
@@ -32,7 +32,7 @@ static void test_bitmap(skiatest::Reporter* reporter) {
     shader->unref();
 
     // test 3: explicitly opaque
-    bmp.setIsOpaque(true);
+    bmp.setAlphaType(kOpaque_SkAlphaType);
     shader = SkShader::CreateBitmapShader(bmp,
         SkShader::kClamp_TileMode, SkShader::kClamp_TileMode);
     REPORTER_ASSERT(reporter, shader);
@@ -40,7 +40,7 @@ static void test_bitmap(skiatest::Reporter* reporter) {
     shader->unref();
 
     // test 4: explicitly not opaque
-    bmp.setIsOpaque(false);
+    bmp.setAlphaType(kPremul_SkAlphaType);
     shader = SkShader::CreateBitmapShader(bmp,
         SkShader::kClamp_TileMode, SkShader::kClamp_TileMode);
     REPORTER_ASSERT(reporter, shader);