Fix encode perf test.

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Change-Id: I7e6b6251b17bc4e74b0197a449ef0313255997e7
diff --git a/test/encode_perf_test.cc b/test/encode_perf_test.cc
index 769e14a..7e9f0d6 100644
--- a/test/encode_perf_test.cc
+++ b/test/encode_perf_test.cc
@@ -189,7 +189,7 @@
         printf("\t\"totalFrames\" : %u,\n", frames);
         printf("\t\"framesPerSecond\" : %f,\n", fps);
         printf("\t\"minPsnr\" : %f,\n", minimum_psnr);
-        printf("\t\"speed\" : %d\n", kEncodePerfTestSpeeds[j]);
+        printf("\t\"speed\" : %d,\n", kEncodePerfTestSpeeds[j]);
         printf("\t\"threads\" : %d\n", kEncodePerfTestThreads[k]);
         printf("}\n");
       }