SkStream::read() only returns 0 at end.

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 41 matching lines @@
 
 // Parse headers of RIFF container, and check for valid Webp (VP8) content.
 static bool webp_parse_header(SkStream* stream, int* width, int* height, int* alpha) {
     unsigned char buffer[WEBP_VP8_HEADER_SIZE];
     size_t bytesToRead = WEBP_VP8_HEADER_SIZE;
     size_t totalBytesRead = 0;
     do {
         unsigned char* dst = buffer + totalBytesRead;
         const size_t bytesRead = stream->read(dst, bytesToRead);
         if (0 == bytesRead) {
-            // Could not read any bytes. Check to see if we are at the end (exit
-            // condition), and continue reading if not. Important for streams
-            // that do not have all the data ready.
-            continue;
+            SkASSERT(stream->isAtEnd());
+            break;
         }
         bytesToRead -= bytesRead;
         totalBytesRead += bytesRead;
         SkASSERT(bytesToRead + totalBytesRead == WEBP_VP8_HEADER_SIZE);
     } while (!stream->isAtEnd() && bytesToRead > 0);
 
     WebPBitstreamFeatures features;
     VP8StatusCode status = WebPGetFeatures(buffer, totalBytesRead, &features);
     if (VP8_STATUS_OK != status) {
         return false; // Invalid WebP file.
@@ skipping 594 matching lines @@
     return SkImageDecoder::kUnknown_Format;
 }
 
 static SkImageEncoder* sk_libwebp_efactory(SkImageEncoder::Type t) {
       return (SkImageEncoder::kWEBP_Type == t) ? SkNEW(SkWEBPImageEncoder) : NULL;
 }
 
 static SkImageDecoder_DecodeReg gDReg(sk_libwebp_dfactory);
 static SkImageDecoder_FormatReg gFormatReg(get_format_webp);
 static SkImageEncoder_EncodeReg gEReg(sk_libwebp_efactory);