Webp has_alpha is a hint only

src/codec/SkWebpCodec.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodecPriv.h"
 #include "SkWebpCodec.h"
 #include "SkTemplates.h"
@@ skipping 72 matching lines @@
             if (SkToBool(features.has_alpha)) {
                 color = SkEncodedInfo::kYUVA_Color;
                 alpha = SkEncodedInfo::kUnpremul_Alpha;
             } else {
                 color = SkEncodedInfo::kYUV_Color;
                 alpha = SkEncodedInfo::kOpaque_Alpha;
             }
             break;
         case 2:
             // This is the lossless format (BGRA).
-            // FIXME: Should we check the has_alpha flag here?  It looks
-            //        like the image is encoded with an alpha channel
-            //        regardless of whether or not the alpha flag is set.
             color = SkEncodedInfo::kBGRA_Color;
             alpha = SkEncodedInfo::kUnpremul_Alpha;
             break;
         default:
             return nullptr;
     }
 
     SkEncodedInfo info = SkEncodedInfo::Make(color, alpha, 8);
     return new SkWebpCodec(features.width, features.height, info, streamDeleter.release());
 }
@@ skipping 165 matching lines @@
             default:
                 return kInvalidInput;
         }
     }
 }
 
 SkWebpCodec::SkWebpCodec(int width, int height, const SkEncodedInfo& info, SkStream* stream)
     // The spec says an unmarked image is sRGB, so we return that space here.
     // TODO: Add support for parsing ICC profiles from webps.
     : INHERITED(width, height, info, stream, SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named)) {}