Simplify image decoder selection.

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

Index: third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
diff --git a/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h b/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
index a41bf4e6d6b75d7d5ee0f9d2eae1ea468fcc6ec6..825458137c29c7b8ad1e0ee9ecdaff7e0657638b 100644
--- a/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
+++ b/third_party/WebKit/Source/platform/image-decoders/ImageDecoder.h
@@ -399,10 +399,6 @@ class PLATFORM_EXPORT ImageDecoder {
   }
 
  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) {