remove unused 'has_alpha' from VP8GetInfo() signature

alpha information is not to be found at RIFF chunks level, not
in the VP8 bitstream (that was a tmp hack)

Change-Id: Idd1629c696b03c26f6f30650d7216f627f1761df

src/dec/idec.c

@@ -281,7 +281,7 @@ static VP8StatusCode DecodeVP8FrameHeader(WebPIDecoder* const idec) {
     // Not enough data bytes to extract VP8 Frame Header.
     return VP8_STATUS_SUSPENDED;
   }
-  if (!VP8GetInfo(data, curr_size, idec->vp8_size_, NULL, NULL, NULL)) {
+  if (!VP8GetInfo(data, curr_size, idec->vp8_size_, NULL, NULL)) {
     return IDecError(idec, VP8_STATUS_BITSTREAM_ERROR);
   }
 

src/dec/vp8.c

@@ -80,14 +80,7 @@ int VP8SetError(VP8Decoder* const dec,
 //------------------------------------------------------------------------------
 
 int VP8GetInfo(const uint8_t* data, uint32_t data_size, uint32_t chunk_size,
-               int* width, int* height, int* has_alpha) {
+               int* width, int* height) {
-  // Alpha-data is stored outside VP8 data and is inferred from VP8X chunk.
-  // So, this function always returns *has_alpha = 0. This value should NOT
-  // be used.
-  if (has_alpha != NULL) {
-    *has_alpha = 0;
-  }
-
   if (data_size < 10) {
     return 0;         // not enough data
   }

src/dec/vp8i.h

@@ -289,12 +289,12 @@ int VP8SetError(VP8Decoder* const dec,
                 VP8StatusCode error, const char * const msg);
 
 // Validates the VP8 data-header and retrieve basic header information viz width
-// and height. Returns 0 in case of formatting error. *width/*height/*has_alpha
+// and height. Returns 0 in case of formatting error. *width/*height
 // can be passed NULL.
 int VP8GetInfo(const uint8_t* data,
                uint32_t data_size,    // data available so far
                uint32_t chunk_size,   // total data size expect in the chunk
-               int *width, int *height, int *has_alpha);
+               int *width, int *height);
 
 // in tree.c
 void VP8ResetProba(VP8Proba* const proba);

src/dec/webp.c

@@ -523,7 +523,7 @@ static VP8StatusCode GetFeatures(const uint8_t* data, uint32_t data_size,
 
   // Validates raw VP8 data.
   if (!VP8GetInfo(data, data_size, vp8_chunk_size,
-                  &features->width, &features->height, NULL)) {
+                  &features->width, &features->height)) {
     return VP8_STATUS_BITSTREAM_ERROR;
   }
 

src/mux/mux.c

@@ -166,7 +166,7 @@ static WebPImageInfo* CreateImageInfo(uint32_t x_offset, uint32_t y_offset,
   int height;
   WebPImageInfo* image_info = NULL;
 
-  if (!VP8GetInfo(data, size, size, &width, &height, NULL)) {
+  if (!VP8GetInfo(data, size, size, &width, &height)) {
     return NULL;
   }
 
@@ -1298,7 +1298,7 @@ static WebPMuxError GetImageCanvasHeightWidth(const WebPMux* const mux,
     const WebPChunk* const image_chunk = wpi->vp8_;
     assert(image_chunk != NULL);
     if (VP8GetInfo(image_chunk->data_, image_chunk->payload_size_,
-                   image_chunk->payload_size_, &w, &h, NULL)) {
+                   image_chunk->payload_size_, &w, &h)) {
       *width = w;
       *height = h;
     }