Remove image decoder and encoder autoregistration

src/images/SkImageDecoder_libpng.h

Index: src/images/SkImageDecoder_libpng.h
diff --git a/src/images/SkImageDecoder_libpng.h b/src/images/SkImageDecoder_libpng.h
new file mode 100644
index 0000000000000000000000000000000000000000..80455b3b449c5f83eafdf5ec99c432006b984f2f
--- /dev/null
+++ b/src/images/SkImageDecoder_libpng.h
@@ -0,0 +1,19 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkPNGImageDecoder_DEFINED
+#define SkPNGImageDecoder_DEFINED
+
+#include "SkImageDecoder.h"
+#include "SkImageEncoder.h"
+
+SkImageDecoder* SkCreatePNGImageDecoder(SkImageDecoder::Format format);
+SkImageDecoder::Format SkDetectFormatPNGImageDecoder(SkStreamRewindable* stream);
+
+SkImageEncoder* SkCreatePNGImageEncoder(SkImageEncoder::Type t);
+
+#endif