Simplify image decoder selection.

third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) Research In Motion Limited 2009-2010. 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 381 matching lines @@
   // used to do alpha blending in WEBPImageDecoder::ApplyPostProcessing().
   //
   // Before calling this, verify that frame |index| exists by checking that
   // |index| is smaller than |frame_buffer_cache_|.size().
   virtual bool FrameStatusSufficientForSuccessors(size_t index) {
     DCHECK(index < frame_buffer_cache_.size());
     return frame_buffer_cache_[index].GetStatus() != ImageFrame::kFrameEmpty;
   }
 
  private:
-  enum class SniffResult { JPEG, PNG, GIF, WEBP, ICO, BMP, kInvalid };
-
-  static SniffResult DetermineImageType(const char* data, size_t length);
-
   // Some code paths compute the size of the image as "width * height * 4"
   // and return it as a (signed) int.  Avoid overflow.
   static bool SizeCalculationMayOverflow(unsigned width, unsigned height) {
     unsigned long long total_size = static_cast<unsigned long long>(width) *
                                     static_cast<unsigned long long>(height);
     return total_size > ((1 << 29) - 1);
   }
 
   bool purge_aggressively_;
 
@@ skipping 12 matching lines @@
   bool has_histogrammed_color_space_ = false;
 
   sk_sp<SkColorSpace> embedded_color_space_ = nullptr;
   bool source_to_target_color_transform_needs_update_ = false;
   std::unique_ptr<SkColorSpaceXform> source_to_target_color_transform_;
 };
 
 }  // namespace blink
 
 #endif