Fix a -Wsign-compare error under GCC 4.9.2.

BUG=

Review URL: https://codereview.chromium.org/1249703005

Cr-Commit-Position: refs/heads/master@{#29795}

test/cctest/test-api.cc

@@ -21029,7 +21029,7 @@ TEST(StreamingWithDebuggingEnabledLate) {
 
   Maybe<uint32_t> result =
       script->Run(env.local()).ToLocalChecked()->Uint32Value(env.local());
-  CHECK_EQ(3, result.FromMaybe(0));
+  CHECK_EQ(3U, result.FromMaybe(0));
 
   delete[] full_source;