Fix SkXfermode deserialization.

tests/SerializationTest.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Resources.h"
 #include "SkBitmapSource.h"
 #include "SkCanvas.h"
@@ skipping 243 matching lines @@
         bitmap.allocN32Pixels(24, 24);
         SkCanvas canvas(bitmap);
         canvas.clear(0x00000000);
         SkPaint paint;
         paint.setImageFilter(deserializedFilter);
         canvas.clipRect(SkRect::MakeXYWH(0, 0, SkIntToScalar(24), SkIntToScalar(24)));
         canvas.drawBitmap(bitmap, 0, 0, &paint);
     }
 }
 
+static void TestXfermodeSerialization(skiatest::Reporter* reporter) {
+    for (size_t i = 0; i <= SkXfermode::kLastMode; ++i) {
+        if (i == SkXfermode::kSrcOver_Mode) {
+            // skip SrcOver, as it is allowed to return NULL from Create()
+            continue;
+        }
+        SkAutoTUnref<SkXfermode> mode(SkXfermode::Create(static_cast<SkXfermode::Mode>(i)));
+        REPORTER_ASSERT(reporter, mode.get());
+        SkAutoTUnref<SkXfermode> copy(
+            TestFlattenableSerialization<SkXfermode>(mode.get(), true, reporter));
+    }
+}
+
 static SkBitmap draw_picture(SkPicture& picture) {
      SkBitmap bitmap;
      bitmap.allocN32Pixels(SkScalarCeilToInt(picture.cullRect().width()), 
                            SkScalarCeilToInt(picture.cullRect().height()));
      SkCanvas canvas(bitmap);
      picture.playback(&canvas);
      return bitmap;
 }
 
 static void compare_bitmaps(skiatest::Reporter* reporter,
@@ skipping 125 matching lines @@
         SkPath path;
         TestObjectSerialization(&path, reporter);
     }
 
     // Test region serialization
     {
         SkRegion region;
         TestObjectSerialization(&region, reporter);
     }
 
+    // Test xfermode serialization
+    {
+        TestXfermodeSerialization(reporter);
+    }
+
     // Test string serialization
     {
         SkString string("string");
         TestObjectSerializationNoAlign<SkString, false>(&string, reporter);
         TestObjectSerializationNoAlign<SkString, true>(&string, reporter);
     }
 
     // Test rrect serialization
     {
         // SkRRect does not initialize anything.
@@ skipping 69 matching lines @@
 
         // Deserialize picture
         SkValidatingReadBuffer reader(static_cast<void*>(data.get()), size);
         SkAutoTUnref<SkPicture> readPict(
             SkPicture::CreateFromBuffer(reader));
         REPORTER_ASSERT(reporter, readPict.get());
     }
 
     TestPictureTypefaceSerialization(reporter);
 }