Remove opaque alpha channel special case

third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.h

 /*
  * Copyright (c) 2008, 2009, 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 223 matching lines @@
   // Returns the value of the desired component (0, 1, 2, 3 == R, G, B, A)
   // in the given pixel data.
   inline unsigned GetComponent(uint32_t pixel, int component) const {
     uint8_t value =
         (pixel & bit_masks_[component]) >> bit_shifts_right_[component];
     return lookup_table_addresses_[component]
                ? lookup_table_addresses_[component][value]
                : value;
   }
 
+  inline bool IsAlphaSupported() const { return bit_masks_[3]; }
+
   inline unsigned GetAlpha(uint32_t pixel) const {
-    // For images without alpha, return alpha of 0xff.
-    return bit_masks_[3] ? GetComponent(pixel, 3) : 0xff;
+    return GetComponent(pixel, 3);

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

Should this

  DCHECK(IsAlphaSupported());

?

[cblume, 2017/05/30 23:45:14]

Good idea.

   }
 
   // Sets the current pixel to the color given by |color_index|.  This also
   // increments the relevant local variables to move the current pixel
   // right by one.
   inline void SetI(size_t color_index) {
     SetRGBA(color_table_[color_index].rgb_red,
             color_table_[color_index].rgb_green,
             color_table_[color_index].rgb_blue, 0xff);
   }
@@ skipping 104 matching lines @@
   // ICOs store a 1bpp "mask" immediately after the main bitmap image data
   // (and, confusingly, add its height to the biHeight value in the info
   // header, thus doubling it). If |is_in_ico_| is true, this variable tracks
   // whether we've begun decoding this mask yet.
   bool decoding_and_mask_;
 };
 
 }  // namespace blink
 
 #endif