Rename UNIT_TEST to WEBRTC_UNIT_TEST

Current name conflicts with upstream project code.

Bug: webrtc:12247
Change-Id: Ibd78273a75262772fc18fca688c29b9ba9525ce5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/196653
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Andrey Logvin <landrey@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32813}
diff --git a/api/units/timestamp.h b/api/units/timestamp.h
index f83477e..1e9f9d1 100644
--- a/api/units/timestamp.h
+++ b/api/units/timestamp.h
@@ -11,9 +11,9 @@
 #ifndef API_UNITS_TIMESTAMP_H_
 #define API_UNITS_TIMESTAMP_H_
 
-#ifdef UNIT_TEST
+#ifdef WEBRTC_UNIT_TEST
 #include <ostream>  // no-presubmit-check TODO(webrtc:8982)
-#endif              // UNIT_TEST
+#endif              // WEBRTC_UNIT_TEST
 
 #include <string>
 #include <type_traits>
@@ -125,13 +125,13 @@
   return ToString(value);
 }
 
-#ifdef UNIT_TEST
+#ifdef WEBRTC_UNIT_TEST
 inline std::ostream& operator<<(  // no-presubmit-check TODO(webrtc:8982)
     std::ostream& stream,         // no-presubmit-check TODO(webrtc:8982)
     Timestamp value) {
   return stream << ToString(value);
 }
-#endif  // UNIT_TEST
+#endif  // WEBRTC_UNIT_TEST
 
 }  // namespace webrtc