Replace CLOCK_MONOTONIC with SYSTEM_TIME_MONOTONIC

Using SYSTEM_TIME_MONOTONIC works for Android (where it translates to
CLOCK_MONOTONIC) and host targets, while CLOCK_MONOTONIC is not defined
on macOS.

Bug: 117921091
Test: existing tests should pass
Change-Id: I1fad472881830fb0701a320cf37319e083932ad4
diff --git a/libs/hwui/renderthread/TimeLord.cpp b/libs/hwui/renderthread/TimeLord.cpp
index b82c5d1..784068f 100644
--- a/libs/hwui/renderthread/TimeLord.cpp
+++ b/libs/hwui/renderthread/TimeLord.cpp
@@ -31,7 +31,7 @@
 
 nsecs_t TimeLord::computeFrameTimeNanos() {
     // Logic copied from Choreographer.java
-    nsecs_t now = systemTime(CLOCK_MONOTONIC);
+    nsecs_t now = systemTime(SYSTEM_TIME_MONOTONIC);
     nsecs_t jitterNanos = now - mFrameTimeNanos;
     if (jitterNanos >= mFrameIntervalNanos) {
         nsecs_t lastFrameOffset = jitterNanos % mFrameIntervalNanos;