Prepare to convert various types to size_t.

webrtc/common_audio/signal_processing/auto_correlation.c

Index: webrtc/common_audio/signal_processing/auto_correlation.c
diff --git a/webrtc/common_audio/signal_processing/auto_correlation.c b/webrtc/common_audio/signal_processing/auto_correlation.c
index 9fb9824eb8fad895f5a7c20add7c1710b6ac3c17..fed131221898c335df78661566c152c5578c8c29 100644
--- a/webrtc/common_audio/signal_processing/auto_correlation.c
+++ b/webrtc/common_audio/signal_processing/auto_correlation.c
@@ -51,7 +51,7 @@ int WebRtcSpl_AutoCorrelation(const int16_t* in_vector,
   for (i = 0; i < order + 1; i++) {
     sum = 0;
     /* Unroll the loop to improve performance. */
-    for (j = 0; j < in_vector_length - i - 3; j += 4) {
+    for (j = 0; i + j + 3 < in_vector_length; j += 4) {
       sum += (in_vector[j + 0] * in_vector[i + j + 0]) >> scaling;
       sum += (in_vector[j + 1] * in_vector[i + j + 1]) >> scaling;
       sum += (in_vector[j + 2] * in_vector[i + j + 2]) >> scaling;