Fix compile warning.

warning: comparison between signed and unsigned integer expressions.

Change-Id: Ib6ee7500fe910983f290fc321ad89c0ab9989455

test/convolve_test.cc

diff --git a/test/convolve_test.cc b/test/convolve_test.cc
index 99bdf82..de947aa 100644
--- a/test/convolve_test.cc
+++ b/test/convolve_test.cc
@@ -22,7 +22,7 @@
 
 namespace {
 
-static const int kMaxDimension = 64;
+static const unsigned int kMaxDimension = 64;
 
 typedef void (*ConvolveFunc)(const uint8_t *src, ptrdiff_t src_stride,
                              uint8_t *dst, ptrdiff_t dst_stride,