Remove opaque alpha channel special case

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

Index: third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.h b/third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.h
index c5bf44b401205a428dcf0f7e6aa4460a2c2221d1..c88a4dd4667bd137939ae287ea3fceab576c9296 100644
--- a/third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.h
+++ b/third_party/WebKit/Source/platform/image-decoders/bmp/BMPImageReader.h
@@ -241,9 +241,11 @@ class PLATFORM_EXPORT BMPImageReader final {
                : 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;
+    DCHECK(IsAlphaSupported());
+    return GetComponent(pixel, 3);
   }
 
   // Sets the current pixel to the color given by |color_index|.  This also