linux: use CLOCK_{REALTIME,MONOTONIC}_COARSE

src/platform/time.h

Index: src/platform/time.h
diff --git a/src/platform/time.h b/src/platform/time.h
index 877e0203bb553920aa6271a81d61695824657891..7e5d59b5a0a5f704582bcc7bc927e2f79bb171b9 100644
--- a/src/platform/time.h
+++ b/src/platform/time.h
@@ -192,6 +192,8 @@ class Time V8_FINAL BASE_EMBEDDED {
   static const int64_t kMicrosecondsPerDay = kMicrosecondsPerHour * 24;
   static const int64_t kMicrosecondsPerWeek = kMicrosecondsPerDay * 7;
   static const int64_t kNanosecondsPerMicrosecond = 1000;
+  static const int64_t kNanosecondsPerMillisecond = kNanosecondsPerMicrosecond *
+                                                    kMicrosecondsPerMillisecond;
   static const int64_t kNanosecondsPerSecond = kNanosecondsPerMicrosecond *
                                                kMicrosecondsPerSecond;