Adding missing command options for zlib_bench

Document the optional compression strategies supported
by zlib_bench.

Bug: 798943
Change-Id: Ic4e1a89163bef087d424467710a016edf5bad242
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2152780Reviewed-by: Chris Blume <cblume@chromium.org>
Reviewed-by: Noel Gordon <noel@chromium.org>
Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#759873}

third_party/zlib/contrib/bench/zlib_bench.cc

@@ -307,7 +307,10 @@ bool get_compression(int argc, char* argv[], int* value) {
 }
 
 void usage_exit(const char* program) {
-  printf("usage: %s gzip|zlib|raw [--compression 0:9] files...\n", program);
+  printf(
+      "usage: %s gzip|zlib|raw [--compression 0:9] [--huffman|--rle] "
+      "files...\n",
+      program);
   exit(1);
 }