Add "use_brotli" flag

- brotli compression of metadata will be optional, so a flag is added to both encoder and decoder
- precomp will pass the flag to Brunsli[Decode/Encode]Jpeg

contrib/brunsli/c/dec/brunsli_decode.cc

@@ -1394,12 +1394,13 @@ BrunsliStatus ProcessJpeg(State* state, JPEGData* jpg) {
 }  // namespace internal
 
 BrunsliStatus BrunsliDecodeJpeg(const uint8_t* data, const size_t len,
-                                JPEGData* jpg) {
+                                JPEGData* jpg, bool use_brotli) {
   if (!data) return BRUNSLI_INVALID_PARAM;
 
   State state;
   state.data = data;
   state.len = len;
+  state.use_brotli = use_brotli;
 
   return internal::dec::ProcessJpeg(&state, jpg);
 }

contrib/brunsli/c/dec/state.h

@@ -81,6 +81,8 @@ struct State {
   bool shallow_histograms = false;
   size_t num_contexts = 0;
   size_t num_histograms = 0;
+
+  bool use_brotli;
 };
 
 // Use in "headerless" mode, after jpg is filled, but before decoding.

contrib/brunsli/c/enc/brunsli_encode.cc

@@ -1371,8 +1371,10 @@ bool BrunsliSerialize(State* state, const JPEGData& jpg, uint32_t skip_sections,
  *
  * For "groups" workflow, few more stages are required, see comments.
  */
-bool BrunsliEncodeJpeg(const JPEGData& jpg, uint8_t* data, size_t* len) {
+bool BrunsliEncodeJpeg(const JPEGData& jpg, uint8_t* data, size_t* len, bool use_brotli) {
   State state;
+  state.use_brotli = use_brotli;
+
   std::vector<ComponentMeta>& meta = state.meta;
   size_t num_components = jpg.components.size();
 

contrib/brunsli/c/enc/state.h

@@ -136,6 +136,8 @@ struct State {
 
   std::vector<ComponentMeta> meta;
   size_t num_contexts;
+
+  bool use_brotli;
 };
 
 // Encoder workflow: