Delete master_timing argument to VCMTiming.

Makes construction simpler, and allows the ts_extrapolator_ pointer
to be marked const.

Followup to https://webrtc-review.googlesource.com/c/src/+/190721

Bug: webrtc:12102
Change-Id: I2abeb960935b5470509f654a4a9d5121c8001900
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/190981
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Commit-Queue: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32535}

modules/video_coding/timing.cc

diff --git a/modules/video_coding/timing.cc b/modules/video_coding/timing.cc
index f1c66b8..eddac4f 100644
--- a/modules/video_coding/timing.cc
+++ b/modules/video_coding/timing.cc
@@ -21,11 +21,11 @@
 
 namespace webrtc {
 
-VCMTiming::VCMTiming(Clock* clock, VCMTiming* master_timing)
+VCMTiming::VCMTiming(Clock* clock)
     : clock_(clock),
-      master_(false),
-      ts_extrapolator_(),
-      codec_timer_(new VCMCodecTimer()),
+      ts_extrapolator_(std::make_unique<TimestampExtrapolator>(
+          clock_->TimeInMilliseconds())),
+      codec_timer_(std::make_unique<VCMCodecTimer>()),
       render_delay_ms_(kDefaultRenderDelayMs),
       min_playout_delay_ms_(0),
       max_playout_delay_ms_(10000),
@@ -37,24 +37,12 @@
       low_latency_renderer_enabled_("enabled", true) {
   ParseFieldTrial({&low_latency_renderer_enabled_},
                   field_trial::FindFullName("WebRTC-LowLatencyRenderer"));
-  if (master_timing == NULL) {
-    master_ = true;
-    ts_extrapolator_ = new TimestampExtrapolator(clock_->TimeInMilliseconds());
-  } else {
-    ts_extrapolator_ = master_timing->ts_extrapolator_;
-  }
-}
-
-VCMTiming::~VCMTiming() {
-  if (master_) {
-    delete ts_extrapolator_;
-  }
 }
 
 void VCMTiming::Reset() {
   MutexLock lock(&mutex_);
   ts_extrapolator_->Reset(clock_->TimeInMilliseconds());
-  codec_timer_.reset(new VCMCodecTimer());
+  codec_timer_ = std::make_unique<VCMCodecTimer>();
   render_delay_ms_ = kDefaultRenderDelayMs;
   min_playout_delay_ms_ = 0;
   jitter_delay_ms_ = 0;
@@ -190,6 +178,8 @@
     // Render as soon as possible or with low-latency renderer algorithm.
     return 0;
   }
+  // Note that TimestampExtrapolator::ExtrapolateLocalTime is not a const
+  // method; it mutates the object's wraparound state.
   int64_t estimated_complete_time_ms =
       ts_extrapolator_->ExtrapolateLocalTime(frame_timestamp);
   if (estimated_complete_time_ms == -1) {

modules/video_coding/timing.h

diff --git a/modules/video_coding/timing.h b/modules/video_coding/timing.h
index 69352de..736b5e9 100644
--- a/modules/video_coding/timing.h
+++ b/modules/video_coding/timing.h
@@ -19,6 +19,7 @@
 #include "rtc_base/experiments/field_trial_parser.h"
 #include "rtc_base/synchronization/mutex.h"
 #include "rtc_base/thread_annotations.h"
+#include "rtc_base/time/timestamp_extrapolator.h"
 
 namespace webrtc {
 
@@ -27,10 +28,8 @@
 
 class VCMTiming {
  public:
-  // The primary timing component should be passed
-  // if this is the dual timing component.
-  explicit VCMTiming(Clock* clock, VCMTiming* master_timing = NULL);
-  virtual ~VCMTiming();
+  explicit VCMTiming(Clock* clock);
+  virtual ~VCMTiming() = default;
 
   // Resets the timing to the initial state.
   void Reset();
@@ -117,8 +116,7 @@
  private:
   mutable Mutex mutex_;
   Clock* const clock_;
-  bool master_ RTC_GUARDED_BY(mutex_);
-  TimestampExtrapolator* ts_extrapolator_ RTC_GUARDED_BY(mutex_)
+  const std::unique_ptr<TimestampExtrapolator> ts_extrapolator_
       RTC_PT_GUARDED_BY(mutex_);
   std::unique_ptr<VCMCodecTimer> codec_timer_ RTC_GUARDED_BY(mutex_)
       RTC_PT_GUARDED_BY(mutex_);