Remove opaque alpha channel special case

third_party/WebKit/Source/platform/graphics/DeferredImageDecoderTest.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 328 matching lines @@
             ColorBehavior::TransformToTargetForTesting());
 
     SkImageInfo pix_info = SkImageInfo::MakeN32Premul(1, 1);
 
     size_t row_bytes = pix_info.minRowBytes();
     size_t size = pix_info.getSafeSize(row_bytes);
 
     Vector<char> storage(size);
     SkPixmap pixmap(pix_info, storage.data(), row_bytes);
 
-    // Before decoding, the frame is not known to be opaque.
+    // Before decoding, the frame's alpha is unknown and assumed to be
+    // transparent. This works well with partial decoding, which will be
+    // transparent until the full first frame is decoded.
     sk_sp<SkImage> frame = decoder->CreateFrameAtIndex(0);
     ASSERT_TRUE(frame);
     EXPECT_FALSE(frame->isOpaque());
 
     // Force a lazy decode by reading pixels.
     EXPECT_TRUE(frame->readPixels(pixmap, 0, 0));
 
-    // After decoding, the frame is known to be opaque.
     frame = decoder->CreateFrameAtIndex(0);
     ASSERT_TRUE(frame);
-    EXPECT_TRUE(frame->isOpaque());
+    // The GIF file specifies it is opaque.
+    // When the file is a PNG (test_gif is false), we remain at

[scroggo_chromium, 2017/05/30 19:45:17]

The comment seems to imply that all PNG files will remain transparent. But I
don't think we want that to be true.

If the PNG file is known to be opaque (e.g. if it's paletted, it does not have
transparent indices, or its type is PNG_COLOR_TYPE_RGB), it should be marked
opaque. This image appears to use PNG_COLOR_TYPE_RGB, so we should've marked it
as opaque.

[cblume, 2017/05/30 23:42:13]

I will try to word it better.
I meant to say that the png file used by this test is transparent.

+    // the default: transparent
+    EXPECT_EQ(test_gif, frame->isOpaque());
 
     // Re-generating the opaque-marked frame should not fail.
     EXPECT_TRUE(frame->readPixels(pixmap, 0, 0));
   }
 }
 
 // The DeferredImageDecoder would sometimes assume that a frame was a certain
 // size even if the actual decoder reported it had a size of 0 bytes. This test
 // verifies that it's fixed by always checking with the actual decoder when
 // creating a frame.
@@ skipping 16 matching lines @@
       SharedBuffer::Create(data_->Data(), data_->size());
   EXPECT_EQ(original_data->size(), data_->size());
   lazy_decoder_->SetData(original_data, false);
   RefPtr<SharedBuffer> new_data = lazy_decoder_->Data();
   EXPECT_EQ(original_data->size(), new_data->size());
   EXPECT_EQ(0, std::memcmp(original_data->Data(), new_data->Data(),
                            new_data->size()));
 }
 
 }  // namespace blink