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

net/quic/platform/impl/quic_chromium_clock.cc

Index: net/quic/platform/impl/quic_chromium_clock.cc
diff --git a/net/quic/platform/impl/quic_chromium_clock.cc b/net/quic/platform/impl/quic_chromium_clock.cc
index fb591f842feffedc69d6145f50771c62b7e1ac14..68c4fc78891bd825599aa66a8d8ba2f97b179b1f 100644
--- a/net/quic/platform/impl/quic_chromium_clock.cc
+++ b/net/quic/platform/impl/quic_chromium_clock.cc
@@ -4,12 +4,6 @@
 
 #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"
 
@@ -29,21 +23,17 @@ QuicTime QuicChromiumClock::ApproximateNow() const {
 }
 
 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());
+  int64_t ticks = (base::TimeTicks::Now() - base::TimeTicks()).InMicroseconds();
+  DCHECK(ticks >= 0);

[Ryan Hamilton, 2017/05/23 19:16:52]

nit: DCHECK_LE(0, ticks);

[kapishnikov, 2017/05/23 19:38:37]

Done. Used DCHECK_GE instead of DCHECK_LE.

+  return CreateTimeFromMicroseconds(ticks);
 }
 
 QuicWallTime QuicChromiumClock::WallNow() const {
-  return QuicWallTime::FromUNIXMicroseconds(base::Time::Now().ToJavaTime() *
-                                            1000);
+  const base::TimeDelta time_since_unix_epoch =
+      base::Time::Now() - base::Time::UnixEpoch();
+  DCHECK(time_since_unix_epoch.InMicroseconds() >= 0);

[Ryan Hamilton, 2017/05/23 19:16:52]

nit: DCHECK_LE(0, time_since_unix_epoch.InMicroseconds());

(or perhaps save InMicroseconds() to a local variable to use in both the DCHECK
and the FromUNIXMicroseconds() call.)

[kapishnikov, 2017/05/23 19:38:37]

Done.

+  return QuicWallTime::FromUNIXMicroseconds(
+      time_since_unix_epoch.InMicroseconds());
 }
 
 }  // namespace net