Remove restart method from VideoTrackSourceInterface.

This method is no longer needed.

Review-Url: https://codereview.webrtc.org/2306013002
Cr-Original-Commit-Position: refs/heads/master@{#14060}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: a973f953863608dab7ac82b35df08cac499a2b0f
diff --git a/api/androidvideotracksource.h b/api/androidvideotracksource.h
index a615b26..79d0df2 100644
--- a/api/androidvideotracksource.h
+++ b/api/androidvideotracksource.h
@@ -37,9 +37,6 @@
   // Not used on Android.
   // TODO(sakal/magjed): Try to remove this from the interface.
   void Stop() override { RTC_NOTREACHED(); };
-  // Not used on Android.
-  // TODO(sakal/magjed): Try to remove this from the interface.
-  void Restart() override { RTC_NOTREACHED(); }
 
   bool is_screencast() const override { return is_screencast_; }
 
diff --git a/api/mediastreaminterface.h b/api/mediastreaminterface.h
index f64d000..33d5e5f 100644
--- a/api/mediastreaminterface.h
+++ b/api/mediastreaminterface.h
@@ -107,7 +107,6 @@
   };
 
   virtual void Stop() = 0;
-  virtual void Restart() = 0;
 
   // Indicates that parameters suitable for screencasts should be automatically
   // applied to RtpSenders.
diff --git a/api/videocapturertracksource.cc b/api/videocapturertracksource.cc
index 2bef143..1bf4bea 100644
--- a/api/videocapturertracksource.cc
+++ b/api/videocapturertracksource.cc
@@ -376,19 +376,6 @@
       rtc::Bind(&cricket::VideoCapturer::Stop, video_capturer_.get()));
 }
 
-void VideoCapturerTrackSource::Restart() {
-  if (started_) {
-    return;
-  }
-  if (!worker_thread_->Invoke<bool>(
-          RTC_FROM_HERE, rtc::Bind(&cricket::VideoCapturer::StartCapturing,
-                                   video_capturer_.get(), format_))) {
-    SetState(kEnded);
-    return;
-  }
-  started_ = true;
-}
-
 // OnStateChange listens to the cricket::VideoCapturer::SignalStateChange.
 void VideoCapturerTrackSource::OnStateChange(
     cricket::VideoCapturer* capturer,
diff --git a/api/videocapturertracksource.h b/api/videocapturertracksource.h
index 92f00dc..e7bbfd2 100644
--- a/api/videocapturertracksource.h
+++ b/api/videocapturertracksource.h
@@ -58,7 +58,6 @@
   bool GetStats(Stats* stats) override;
 
   void Stop() override;
-  void Restart() override;
 
  protected:
   VideoCapturerTrackSource(rtc::Thread* worker_thread,
diff --git a/api/videocapturertracksource_unittest.cc b/api/videocapturertracksource_unittest.cc
index 90d2cd2..607188c 100644
--- a/api/videocapturertracksource_unittest.cc
+++ b/api/videocapturertracksource_unittest.cc
@@ -157,30 +157,6 @@
                  kMaxWaitMs);
 }
 
-// Test that a VideoSource can be stopped and restarted.
-TEST_F(VideoCapturerTrackSourceTest, StopRestart) {
-  // Initialize without constraints.
-  CreateVideoCapturerSource();
-  EXPECT_EQ_WAIT(MediaSourceInterface::kLive, state_observer_->state(),
-                 kMaxWaitMs);
-
-  ASSERT_TRUE(capturer_->CaptureFrame());
-  EXPECT_EQ(1, renderer_.num_rendered_frames());
-
-  source_->Stop();
-  EXPECT_EQ_WAIT(MediaSourceInterface::kEnded, state_observer_->state(),
-                 kMaxWaitMs);
-
-  source_->Restart();
-  EXPECT_EQ_WAIT(MediaSourceInterface::kLive, state_observer_->state(),
-                 kMaxWaitMs);
-
-  ASSERT_TRUE(capturer_->CaptureFrame());
-  EXPECT_EQ(2, renderer_.num_rendered_frames());
-
-  source_->Stop();
-}
-
 // Test that a VideoSource transition to kEnded if the capture device
 // fails.
 TEST_F(VideoCapturerTrackSourceTest, CameraFailed) {
diff --git a/api/videosourceproxy.h b/api/videosourceproxy.h
index 6d4dfcb..40f81dc 100644
--- a/api/videosourceproxy.h
+++ b/api/videosourceproxy.h
@@ -24,7 +24,6 @@
   PROXY_CONSTMETHOD0(SourceState, state)
   PROXY_CONSTMETHOD0(bool, remote)
   PROXY_METHOD0(void, Stop)
-  PROXY_METHOD0(void, Restart)
   PROXY_CONSTMETHOD0(bool, is_screencast)
   PROXY_CONSTMETHOD0(rtc::Optional<bool>, needs_denoising)
   PROXY_METHOD1(bool, GetStats, Stats*)
diff --git a/api/videotracksource.h b/api/videotracksource.h
index 10e24ab..1d1d579 100644
--- a/api/videotracksource.h
+++ b/api/videotracksource.h
@@ -34,7 +34,6 @@
   bool remote() const override { return remote_; }
 
   void Stop() override{};
-  void Restart() override{};
 
   bool is_screencast() const override { return false; }
   rtc::Optional<bool> needs_denoising() const override {