store SkAlphaType inside SkBitmap, on road to support unpremul

tests/BitmapCopyTest.cpp

Index: tests/BitmapCopyTest.cpp
diff --git a/tests/BitmapCopyTest.cpp b/tests/BitmapCopyTest.cpp
index 88ce577f682aa974c60b54081829c3f9e4fc0382..c6664261da4ad575cab8cc0ae2ac203cc48fd817 100644
--- a/tests/BitmapCopyTest.cpp
+++ b/tests/BitmapCopyTest.cpp
@@ -43,7 +43,7 @@ static void test_isOpaque(skiatest::Reporter* reporter, const SkBitmap& src,
     unsigned ctableFlags = ctable ? ctable->getFlags() : 0;
 
     if (canHaveAlpha(bitmap.config()) && canHaveAlpha(dstConfig)) {
-        bitmap.setIsOpaque(false);
+        bitmap.setAlphaType(kPremul_SkAlphaType);
         if (ctable) {
             ctable->setFlags(ctableFlags & ~SkColorTable::kColorsAreOpaque_Flag);
         }
@@ -54,7 +54,7 @@ static void test_isOpaque(skiatest::Reporter* reporter, const SkBitmap& src,
         }
     }
 
-    bitmap.setIsOpaque(true);
+    bitmap.setAlphaType(kOpaque_SkAlphaType);
     if (ctable) {
         ctable->setFlags(ctableFlags | SkColorTable::kColorsAreOpaque_Flag);
     }
@@ -311,7 +311,7 @@ static void TestBitmapCopy(skiatest::Reporter* reporter) {
                     SkBitmap subset;
                     SkIRect r;
                     r.set(1, 1, 2, 2);
-                    bitmap.setIsOpaque(true);
+                    bitmap.setAlphaType(kOpaque_SkAlphaType);
                     bitmap.setIsVolatile(true);
                     if (bitmap.extractSubset(&subset, r)) {
                         REPORTER_ASSERT(reporter, subset.width() == 1);
@@ -335,7 +335,7 @@ static void TestBitmapCopy(skiatest::Reporter* reporter) {
                         REPORTER_ASSERT(reporter,
                                     (copy.getColorTable() != NULL) == hasCT);
                     }
-                    bitmap.setIsOpaque(false);
+                    bitmap.setAlphaType(kPremul_SkAlphaType);
                     bitmap.setIsVolatile(false);
                     if (bitmap.extractSubset(&subset, r)) {
                         REPORTER_ASSERT(reporter,