Remove opaque alpha channel special case

third_party/WebKit/Source/platform/image-decoders/webp/WEBPImageDecoder.cpp

 /*
  * Copyright (C) 2010 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 239 matching lines @@
     const ImageFrame& prev_buffer =
         frame_buffer_cache_[required_previous_frame_index];
     frame_background_has_alpha_ =
         prev_buffer.HasAlpha() || (prev_buffer.GetDisposalMethod() ==
                                    ImageFrame::kDisposeOverwriteBgcolor);
   }
 
   // The buffer is transparent outside the decoded area while the image is
   // loading. The correct alpha value for the frame will be set when it is fully
   // decoded.
   buffer.SetHasAlpha(true);

[scroggo_chromium, 2017/05/31 14:27:50]

If we're going to remove the other call to SetHasAlpha (which is used for single
frame images), shouldn't we also remove this one (which is used for multi-frame
images)?

 }
 
 bool WEBPImageDecoder::CanReusePreviousFrameBuffer(size_t frame_index) const {
   DCHECK(frame_index < frame_buffer_cache_.size());
   return frame_buffer_cache_[frame_index].GetAlphaBlendSource() !=
          ImageFrame::kBlendAtopPreviousFrame;
 }
 
 void WEBPImageDecoder::ClearFrameBuffer(size_t frame_index) {
   if (demux_ && demux_state_ >= WEBP_DEMUX_PARSED_HEADER &&
@@ skipping 186 matching lines @@
 
   DCHECK_GT(frame_buffer_cache_.size(), frame_index);
   ImageFrame& buffer = frame_buffer_cache_[frame_index];
   DCHECK_NE(buffer.GetStatus(), ImageFrame::kFrameComplete);
 
   if (buffer.GetStatus() == ImageFrame::kFrameEmpty) {
     if (!buffer.AllocatePixelData(Size().Width(), Size().Height(),
                                   ColorSpaceForSkImages()))
       return SetFailed();
     buffer.ZeroFillPixelData();
-    buffer.SetStatus(ImageFrame::kFramePartial);
     // The buffer is transparent outside the decoded area while the image is
     // loading. The correct alpha value for the frame will be set when it is
     // fully decoded.
-    buffer.SetHasAlpha(true);
+    buffer.SetStatus(ImageFrame::kFramePartial);
     buffer.SetOriginalFrameRect(IntRect(IntPoint(), Size()));
   }
 
   const IntRect& frame_rect = buffer.OriginalFrameRect();
   if (!decoder_) {
     WEBP_CSP_MODE mode = outputMode(format_flags_ & ALPHA_FLAG);
     if (!premultiply_alpha_)
       mode = outputMode(false);
     if (ColorTransform()) {
       // Swizzling between RGBA and BGRA is zero cost in a color transform.
@@ skipping 34 matching lines @@
         return false;
       }
     // FALLTHROUGH
     default:
       Clear();
       return SetFailed();
   }
 }
 
 }  // namespace blink