[M114-LTS] Fix OOB write in BuildHuffmanTable.

M114 merge issues:
  dec/vp8l_dec.c:
    - Conflicting checks before ReadHuffmanCodeLengths() return statement;
    In 114, an assignment follows the check instead of a return.
    - ReadHuffmanCodes(): Conflict after the changed huffman_tables check,
    there's an assignment in 114 instead of the setter call.

First, BuildHuffmanTable is called to check if the data is valid.
If it is and the table is not big enough, more memory is allocated.

This will make sure that valid (but unoptimized because of unbalanced
codes) streams are still decodable.

Bug: chromium:1479274
Change-Id: I31c36dbf3aa78d35ecf38706b50464fd3d375741
(cherry picked from commit 902bc91903)

src/enc/alpha_enc.c

@@ -141,11 +141,6 @@ static int EncodeAlphaInternal(const uint8_t* const data, int width, int height,
                               !reduce_levels, &tmp_bw, &result->stats);
     if (ok) {
       output = VP8LBitWriterFinish(&tmp_bw);
-      if (tmp_bw.error_) {
-        VP8LBitWriterWipeOut(&tmp_bw);
-        memset(&result->bw, 0, sizeof(result->bw));
-        return 0;
-      }
       output_size = VP8LBitWriterNumBytes(&tmp_bw);
       if (output_size > data_size) {
         // compressed size is larger than source! Revert to uncompressed mode.

src/enc/vp8l_enc.c

@@ -1449,11 +1449,6 @@ static int WriteImage(const WebPPicture* const pic, VP8LBitWriter* const bw,
   const size_t vp8l_size = VP8L_SIGNATURE_SIZE + webpll_size;
   const size_t pad = vp8l_size & 1;
   const size_t riff_size = TAG_SIZE + CHUNK_HEADER_SIZE + vp8l_size + pad;
-  *coded_size = 0;
-
-  if (bw->error_) {
-    return WebPEncodingSetError(pic, VP8_ENC_ERROR_OUT_OF_MEMORY);
-  }
 
   if (!WriteRiffHeader(pic, riff_size, vp8l_size) ||
       !pic->writer(webpll_data, webpll_size, pic)) {