Silence compiler warning.

warning: comparison between signed and unsigned integer expressions


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92359 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/unittests/ADT/StringRefTest.cpp b/unittests/ADT/StringRefTest.cpp
index 8507efa..b0dcb0a 100644
--- a/unittests/ADT/StringRefTest.cpp
+++ b/unittests/ADT/StringRefTest.cpp
@@ -249,7 +249,7 @@
 
 TEST(StringRefTest, EditDistance) {
   StringRef Str("hello");
-  EXPECT_EQ(2, Str.edit_distance("hill"));
+  EXPECT_EQ(2U, Str.edit_distance("hill"));
 }
 
 TEST(StringRefTest, Misc) {