Fix unsigned/signed comparison warning.

llvm-svn: 227158
diff --git a/llvm/unittests/Support/ConvertUTFTest.cpp b/llvm/unittests/Support/ConvertUTFTest.cpp
index a6dbe4c..d436fc0 100644
--- a/llvm/unittests/Support/ConvertUTFTest.cpp
+++ b/llvm/unittests/Support/ConvertUTFTest.cpp
@@ -46,7 +46,7 @@
   bool Success = convertUTF8ToUTF16String(Ref, Result);
   EXPECT_TRUE(Success);
   static const UTF16 Expected[] = {0x0CA0, 0x005f, 0x0CA0, 0};
-  ASSERT_EQ(3, Result.size());
+  ASSERT_EQ(3u, Result.size());
   for (int I = 0, E = 3; I != E; ++I)
     EXPECT_EQ(Expected[I], Result[I]);
 }