Add Chromium-style TimeDelta, Time and TimeTicks classes, and a new ElapsedTimer class.

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index 1244493593b4db44aa67ab9def68b1e433a88d07..5ef92b14ac448232fb7dec6eca2fb5a378066393 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -318,19 +318,7 @@ int OS::GetUserTime(uint32_t* secs,  uint32_t* usecs) {
 
 
 double OS::TimeCurrentMillis() {
-  struct timeval tv;
-  if (gettimeofday(&tv, NULL) < 0) return 0.0;
-  return (static_cast<double>(tv.tv_sec) * 1000) +
-         (static_cast<double>(tv.tv_usec) / 1000);
-}
-
-
-int64_t OS::Ticks() {
-  // gettimeofday has microsecond resolution.
-  struct timeval tv;
-  if (gettimeofday(&tv, NULL) < 0)
-    return 0;
-  return (static_cast<int64_t>(tv.tv_sec) * 1000000) + tv.tv_usec;
+  return Time::Now().ToJsTime();
 }