Rename USE_NATIVE_MUTEX_ON_MAC to RTC_USE_NATIVE_MUTEX_ON_MAC.

WebRTC internal macros should be prefixed by RTC_.

Bug: None
Change-Id: I1a0be41ca1ea35173edf34bc190fc425c5f2c67b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/144782
Commit-Queue: Steve Anton <steveanton@webrtc.org>
Reviewed-by: Steve Anton <steveanton@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28509}
diff --git a/rtc_base/critical_section.h b/rtc_base/critical_section.h
index 4433529..f9047a6 100644
--- a/rtc_base/critical_section.h
+++ b/rtc_base/critical_section.h
@@ -34,9 +34,9 @@
 #endif
 
 // See notes in the 'Performance' unit test for the effects of this flag.
-#define USE_NATIVE_MUTEX_ON_MAC 1
+#define RTC_USE_NATIVE_MUTEX_ON_MAC 1
 
-#if defined(WEBRTC_MAC) && !USE_NATIVE_MUTEX_ON_MAC
+#if defined(WEBRTC_MAC) && !RTC_USE_NATIVE_MUTEX_ON_MAC
 #include <dispatch/dispatch.h>
 #endif
 
@@ -61,7 +61,7 @@
 #if defined(WEBRTC_WIN)
   mutable CRITICAL_SECTION crit_;
 #elif defined(WEBRTC_POSIX)
-#if defined(WEBRTC_MAC) && !USE_NATIVE_MUTEX_ON_MAC
+#if defined(WEBRTC_MAC) && !RTC_USE_NATIVE_MUTEX_ON_MAC
   // Number of times the lock has been locked + number of threads waiting.
   // TODO(tommi): We could use this number and subtract the recursion count
   // to find places where we have multiple threads contending on the same lock.