Have only two pure virtual methods for webrtc::Clock,

`CurrentTime` and `CurrentNtpTime`. Make all other methods non-virtual.

Bug: webrtc:11327
Change-Id: I391d9eaec1ba27ec4f8e1901498c68c28a7ec4ff
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/219466
Reviewed-by: Niels Moller <nisse@webrtc.org>
Commit-Queue: Paul Hallak <phallak@google.com>
Cr-Commit-Position: refs/heads/master@{#34065}

system_wrappers/include/clock.h

@@ -34,22 +34,13 @@ class RTC_EXPORT Clock {
   virtual ~Clock() {}
 
   // Return a timestamp relative to an unspecified epoch.
-  // TODO(bugs.webrtc.org/11327): Make this a pure virtual function.
+  virtual Timestamp CurrentTime() = 0;
-  virtual Timestamp CurrentTime() {
+  int64_t TimeInMilliseconds() { return CurrentTime().ms(); }
-    return Timestamp::Micros(TimeInMicroseconds());
+  int64_t TimeInMicroseconds() { return CurrentTime().us(); }
-  }
-
-  // TODO(bugs.webrtc.org/11327): Make the following two methods non-virtual
-  // or completely remove them.
-  virtual int64_t TimeInMilliseconds() { return CurrentTime().ms(); }
-  virtual int64_t TimeInMicroseconds() { return CurrentTime().us(); }
 
   // Retrieve an NTP absolute timestamp (with an epoch of Jan 1, 1900).
   virtual NtpTime CurrentNtpTime() = 0;
-
+  int64_t CurrentNtpInMilliseconds() { return CurrentNtpTime().ToMs(); }
-  // TODO(bugs.webrtc.org/11327): Make the following method non-virtual
-  // or completely remove it.
-  virtual int64_t CurrentNtpInMilliseconds() { return CurrentNtpTime().ToMs(); }
 
   // Returns an instance of the real-time system clock implementation.
   static Clock* GetRealTimeClock();

test/drifting_clock.cc

@@ -42,8 +42,5 @@ NtpTime DriftingClock::CurrentNtpTime() {
   return NtpTime(total_fractions);
 }
 
-int64_t DriftingClock::CurrentNtpInMilliseconds() {
-  return clock_->CurrentNtpInMilliseconds() + Drift().ms();
-}
 }  // namespace test
 }  // namespace webrtc

test/drifting_clock.h

@@ -32,7 +32,6 @@ class DriftingClock : public Clock {
 
   Timestamp CurrentTime() override;
   NtpTime CurrentNtpTime() override;
-  int64_t CurrentNtpInMilliseconds() override;
 
  private:
   TimeDelta Drift() const;