Remove opaque alpha channel special case

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

Index: third_party/WebKit/Source/platform/graphics/DeferredImageDecoderTest.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/DeferredImageDecoderTest.cpp b/third_party/WebKit/Source/platform/graphics/DeferredImageDecoderTest.cpp
index 905b2d3830a6bff94ca44cb1de4d2cbbbd979b13..b8b6bcc9dd3740ee1031d622d2e19e57df55e47c 100644
--- a/third_party/WebKit/Source/platform/graphics/DeferredImageDecoderTest.cpp
+++ b/third_party/WebKit/Source/platform/graphics/DeferredImageDecoderTest.cpp
@@ -346,7 +346,9 @@ TEST_F(DeferredImageDecoderTest, frameOpacity) {
     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());
@@ -354,10 +356,12 @@ TEST_F(DeferredImageDecoderTest, frameOpacity) {
     // 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));