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 95 matching lines @@
     }
 
     virtual Format getFormat() const SK_OVERRIDE {
         return kWEBP_Format;
     }
 
 protected:
     virtual bool onBuildTileIndex(SkStream *stream, int *width, int *height) SK_OVERRIDE;
     virtual bool onDecodeRegion(SkBitmap* bitmap, const SkIRect& rect) SK_OVERRIDE;
     virtual bool onDecode(SkStream* stream, SkBitmap* bm, Mode) SK_OVERRIDE;
+    virtual Format onGetFormat(SkStream*) const SK_OVERRIDE;
 
 private:
     bool setDecodeConfig(SkBitmap* decodedBitmap, int width, int height);
     SkStream* fInputStream;
     int fOrigWidth;
     int fOrigHeight;
     int fHasAlpha;
 
     typedef SkImageDecoder INHERITED;
 };
 
+SkImageDecoder::Format SkWEBPImageDecoder::onGetFormat(SkStream* stream) const {
+    int width, height, hasAlpha;
+    if (webp_parse_header(stream, &width, &height, &hasAlpha)) {
+        return kWEBP_Format;
+    }
+    return kUnknown_Format;
+}
+
 //////////////////////////////////////////////////////////////////////////
 
 #ifdef TIME_DECODE
 
 #include "SkTime.h"
 
 class AutoTimeMillis {
 public:
     AutoTimeMillis(const char label[]) :
         fLabel(label) {
@@ skipping 449 matching lines @@
     // Magic matches, call decoder
     return SkNEW(SkWEBPImageDecoder);
 }
 
 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<SkImageEncoder*, SkImageEncoder::Type> gEReg(sk_libwebp_efactory);