Updates to skimage tool to use it for testing.

src/images/SkImageDecoder_libwebp.cpp

 /*
  * Copyright 2010, The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
@@ skipping 569 matching lines @@
 static SkImageDecoder* sk_libwebp_dfactory(SkStream* stream) {
     int width, height, hasAlpha;
     if (!webp_parse_header(stream, &width, &height, &hasAlpha)) {
         return NULL;
     }
 
     // Magic matches, call decoder
     return SkNEW(SkWEBPImageDecoder);
 }
 
+static SkImageDecoder::Format get_format_webp(SkStream* stream) {
+    int width, height, hasAlpha;
+    if (webp_parse_header(stream, &width, &height, &hasAlpha)) {
+        return SkImageDecoder::kWEBP_Format;
+    }
+    return SkImageDecoder::kUnknown_Format;
+}
+
 static SkImageEncoder* sk_libwebp_efactory(SkImageEncoder::Type t) {
       return (SkImageEncoder::kWEBP_Type == t) ? SkNEW(SkWEBPImageEncoder) : NULL;
 }
 
 static SkTRegistry<SkImageDecoder*, SkStream*> gDReg(sk_libwebp_dfactory);
+static SkTRegistry<SkImageDecoder::Format, SkStream*> gFormatReg(get_format_webp);
 static SkTRegistry<SkImageEncoder*, SkImageEncoder::Type> gEReg(sk_libwebp_efactory);