Use demux API in SkWebpCodec

tests/CodecTest.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Resources.h"
 #include "SkAndroidCodec.h"
 #include "SkBitmap.h"
@@ skipping 861 matching lines @@
     size_t peek(void* buf, size_t bytes) const override {
         return fStream.peek(buf, SkTMin(bytes, fLimit));
     }
     size_t read(void* buf, size_t bytes) override {
         return fStream.read(buf, bytes);
     }
     bool rewind() override {
         return fStream.rewind();
     }
     bool isAtEnd() const override {
-        return false;
+        return fStream.isAtEnd();
     }
 private:
     SkMemoryStream fStream;
     const size_t   fLimit;
 };
 
 // Stream that is not an asset stream (!hasPosition() or !hasLength())
 class NotAssetMemStream : public SkStream {
 public:
     NotAssetMemStream(sk_sp<SkData> data) : fStream(std::move(data)) {}
@@ skipping 220 matching lines @@
     // Create an arbitrary gray bitmap.
     path = "grayscale.jpg";
     stream.reset(resource(path));
     codec.reset(SkCodec::NewFromStream(stream.release()));
     SkBitmap bm2;
     bm2.allocPixels(codec->getInfo());
     result = codec->getPixels(codec->getInfo(), bm2.getPixels(), bm2.rowBytes());
     REPORTER_ASSERT(r, SkCodec::kSuccess == result);
     check_round_trip(r, bm2);
 }