Fix encode perf test

The accepted range changed to -8..8.
BUG:https://code.google.com/p/webm/issues/detail?id=901

Change-Id: I53ac80b58f4819b82c76db61db5dc476f821191f

test/encode_perf_test.cc

@@ -50,7 +50,7 @@ const EncodePerfTestVideo kVP9EncodePerfTestVectors[] = {
   EncodePerfTestVideo("niklas_1280_720_30.yuv", 1280, 720, 600, 470),
 };
 
-const int kEncodePerfTestSpeeds[] = { 5, 6, 7, 12 };
+const int kEncodePerfTestSpeeds[] = { 5, 6, 7, 8 };
 
 #define NELEMENTS(x) (sizeof((x)) / sizeof((x)[0]))