Write protos as binary.

We need to write protos as "wb" and not "w", otherwise we get CRLF
on Windows which corrupts the proto.

Bug: chromium:1029452
Change-Id: Iabf841405134d7bc2523ac48219ca7cb9d8214c1
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/170320
Commit-Queue: Patrik Höglund <phoglund@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30772}

modules/audio_coding/codecs/isac/fix/test/kenny.cc

@@ -861,7 +861,7 @@ TEST(IsacFixTest, Kenny) {
                             (runtime * 10000) / length_file, "us", false);
 
   if (chartjson_result_file) {
-    webrtc::test::WritePerfResults(chartjson_result_file);
+    EXPECT_TRUE(webrtc::test::WritePerfResults(chartjson_result_file));
   }
 
   fclose(inp);