Make is_ktx safer

src/images/SkKTXImageEncoder.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColorPriv.h"
 #include "SkImageEncoder.h"
 #include "SkImageGenerator.h"
@@ skipping 38 matching lines @@
     SkAutoDataUnref data(bitmap.pixelRef()->refEncodedData());
 
     // Is this even encoded data?
     if (data) {
         const uint8_t *bytes = data->bytes();
         if (etc1_pkm_is_valid(bytes)) {
             return this->encodePKM(stream, data);
         }
 
         // Is it a KTX file??
-        if (SkKTXFile::is_ktx(bytes)) {
+        if (SkKTXFile::is_ktx(bytes, data->size())) {
             return stream->write(bytes, data->size());
         }
 
         // If it's neither a KTX nor a PKM, then we need to
         // get at the actual pixels, so fall through and decompress...
     }
 
     return SkKTXFile::WriteBitmapToKTX(stream, bitmap);
 }
 
@@ skipping 18 matching lines @@
 
 /////////////////////////////////////////////////////////////////////////////////////////
 DEFINE_ENCODER_CREATOR(KTXImageEncoder);
 /////////////////////////////////////////////////////////////////////////////////////////
 
 SkImageEncoder* sk_libktx_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kKTX_Type == t) ? new SkKTXImageEncoder : nullptr;
 }
 
 static SkImageEncoder_EncodeReg gEReg(sk_libktx_efactory);