Revert of Use CLOCK_REALTIME_COARSE when available. (patchset #1 id:1 of...

Revert of Use CLOCK_REALTIME_COARSE when available. (patchset #1 id:1 of https://codereview.chromium.org/1151283005/)

Reason for revert:
[Sheriff] This leads to several failures in chromium and blocks our roll:
https://codereview.chromium.org/1154363002/

Bisect (https://codereview.chromium.org/1152553004/) points to this CL.

Please add the failing chromium trybot on a reland of this CL.

Original issue's description:
> Use CLOCK_REALTIME_COARSE when available.
>
> On systems that have CLOCK_REALTIME_COARSE with good enough resolution,
> we can avoid making a system call to get the current time; it's serviced
> from the vDSO.
>
> This is v2 of the patch.  v1 can be found at [0] but was reverted in [1]
> because of Chromium sandbox restrictions.  The necessary changes have
> been applied upstream in [2].
>
> [0] https://codereview.chromium.org/1125003002
> [1] https://codereview.chromium.org/1130083003
> [2] https://codereview.chromium.org/1133653002
>
> BUG=
> LOG=N
>
> Committed: https://crrev.com/28cea2b749f24ba33e6e0c8e343dd0d6258ee302
> Cr-Commit-Position: refs/heads/master@{#28639}

TBR=jochen@chromium.org,bmeurer@chromium.org,ben@strongloop.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Review URL: https://codereview.chromium.org/1154783003

Cr-Commit-Position: refs/heads/master@{#28656}

src/base/platform/time.cc

@@ -20,16 +20,10 @@
 #include "src/base/lazy-instance.h"
 #include "src/base/win32-headers.h"
 #endif
-#include "src/base/atomicops.h"
 #include "src/base/cpu.h"
 #include "src/base/logging.h"
 #include "src/base/platform/platform.h"
 
-// CLOCK_REALTIME_COARSE was added in Linux 2.6.32.
-#if V8_OS_LINUX && !defined(CLOCK_REALTIME_COARSE)
-#define CLOCK_REALTIME_COARSE 5
-#endif
-
 namespace v8 {
 namespace base {
 
@@ -258,40 +252,11 @@ FILETIME Time::ToFiletime() const {
 #elif V8_OS_POSIX
 
 Time Time::Now() {
-#ifdef CLOCK_REALTIME_COARSE
-  struct timespec ts;
-  static const clockid_t kInvalidClockId = static_cast<clockid_t>(-1);
-  static clockid_t cached_clock_id = kInvalidClockId;
-  clockid_t clock_id = NoBarrier_Load(&cached_clock_id);
-  if (V8_UNLIKELY(clock_id == kInvalidClockId)) {
-    // Use CLOCK_REALTIME_COARSE when available (linux >= 2.6.32) and precise
-    // enough.  Unlike CLOCK_REALTIME, its coarse cousin is normally serviced
-    // from the vDSO, without making an actual system call.
-    //
-    // CLOCK_REALTIME_COARSE precision is determined by CONFIG_HZ, the number
-    // of ticks per second that the kernel runs at.  Granularity can be as low
-    // as one update every few hundred milliseconds so we need to ensure it is
-    // not _too_ coarse.  Most kernels are built with CONFIG_HZ=1000, providing
-    // a one millisecond precision that is good enough for our purposes.
-    if (clock_getres(CLOCK_REALTIME_COARSE, &ts) < 0 || ts.tv_sec > 0 ||
-        ts.tv_nsec > 1000 * 1000) {
-      clock_id = CLOCK_REALTIME;  // Not available or not suitable.
-    } else {
-      clock_id = CLOCK_REALTIME_COARSE;
-    }
-    NoBarrier_Store(&cached_clock_id, clock_id);
-  }
-  int result = clock_gettime(clock_id, &ts);
-  DCHECK_EQ(0, result);
-  USE(result);
-  return FromTimespec(ts);
-#else
   struct timeval tv;
   int result = gettimeofday(&tv, NULL);
   DCHECK_EQ(0, result);
   USE(result);
   return FromTimeval(tv);
-#endif
 }