Use faster clock_gettime() instead of sysctl() to get current ticks on iOS10

net/quic/platform/impl/quic_chromium_clock.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/platform/impl/quic_chromium_clock.h"
 
-#if defined(OS_IOS)
-#include <time.h>
-
-#include "base/ios/ios_util.h"
-#endif
-
 #include "base/memory/singleton.h"
 #include "base/time/time.h"
 
 namespace net {
 
 QuicChromiumClock* QuicChromiumClock::GetInstance() {
   return base::Singleton<QuicChromiumClock>::get();
 }
 QuicChromiumClock::QuicChromiumClock() {}
 
 QuicChromiumClock::~QuicChromiumClock() {}
 
 QuicTime QuicChromiumClock::ApproximateNow() const {
   // At the moment, Chrome does not have a distinct notion of ApproximateNow().
   // We should consider implementing this using MessageLoop::recent_time_.
   return Now();
 }
 
 QuicTime QuicChromiumClock::Now() const {
-#if defined(OS_IOS)
-  if (base::ios::IsRunningOnIOS10OrLater()) {
-    struct timespec tp;
-    if (clock_gettime(CLOCK_MONOTONIC, &tp) == 0) {
-      return CreateTimeFromMicroseconds(tp.tv_sec * 1000000 +
-                                        tp.tv_nsec / 1000);
-    }
-  }
-#endif
   return CreateTimeFromMicroseconds(base::TimeTicks::Now().ToInternalValue());

[miu, 2017/05/22 22:16:14]

Please fix: This is invalid use of ToInternalValue() (and ToInternalValue() is
deprecated). If you want an arbitrary tick count in a microsecond timebase, you
should make this:

  return CreateTimeFromMicroseconds(
      (base::TimeTicks::Now() - base::TimeTicks()).InMicroseconds());

More info: http://crbug.com/634507

[kapishnikov, 2017/05/23 17:56:51]

Done.

 }
 
 QuicWallTime QuicChromiumClock::WallNow() const {
   return QuicWallTime::FromUNIXMicroseconds(base::Time::Now().ToJavaTime() *

[miu, 2017/05/22 22:16:14]

Please fix: You are using a platform conversion function where there is no
platform converting being done. This should be something like:

  const base::TimeDelta time_since_unix_epoch =
      base::Time::Now() - base::Time::UnixEpoch();
  return QuicWallTime::FromUNIXMicroseconds(
      time_since_unix_epoch.InMicroseconds());

Note: The existing code here always truncates to millisecond precision, which is
probably not a good idea; but I don't fully understand the use case of this
function, so I leave it up to you to decide whether that's a good idea. If so,
please use TimeDelta's operator%() to subtract-out the sub-millisecond
component. 

Note 2: https://codereview.chromium.org/2892553005/

More info: Please see discussion in https://codereview.chromium.org/2870223003/.
It's on me (on my TODO list) to take discussions like these and put together a
"best practices" document. ;)

[kapishnikov, 2017/05/23 17:56:51]

Done. I think it was truncated to milliseconds because the wall-time in Java is
measured in milliseconds since January 1, 1970 UTC. I don't think truncating
makes sense.

                                             1000);
 }
 
 }  // namespace net