Remove cricket::VideoFrame::Set/GetElapsedTime()

talk/app/webrtc/objc/avfoundationvideocapturer.mm

Index: talk/app/webrtc/objc/avfoundationvideocapturer.mm
diff --git a/talk/app/webrtc/objc/avfoundationvideocapturer.mm b/talk/app/webrtc/objc/avfoundationvideocapturer.mm
index c47e36dc40930d784756d7364569e19bd6401f38..b4d7ee2443e083f0eed876629ea1115f07cc2c7c 100644
--- a/talk/app/webrtc/objc/avfoundationvideocapturer.mm
+++ b/talk/app/webrtc/objc/avfoundationvideocapturer.mm
@@ -306,7 +306,7 @@ static dispatch_queue_t kBackgroundQueue = nil;
 namespace webrtc {
 
 AVFoundationVideoCapturer::AVFoundationVideoCapturer()
-    : _capturer(nil), _startThread(nullptr), _startTime(0) {
+    : _capturer(nil), _startThread(nullptr) {
   // Set our supported formats. This matches kDefaultPreset.
   std::vector<cricket::VideoFormat> supportedFormats;
   supportedFormats.push_back(cricket::VideoFormat(kDefaultFormat));
@@ -344,7 +344,6 @@ cricket::CaptureState AVFoundationVideoCapturer::Start(
   // to spin up, and this call returns async.
   // TODO(tkchin): make this better.
   [_capturer startCaptureAsync];
-  _startTime = rtc::TimeNanos();
   SetCaptureState(cricket::CaptureState::CS_RUNNING);
 
   return cricket::CaptureState::CS_STARTING;
@@ -424,7 +423,6 @@ void AVFoundationVideoCapturer::CaptureSampleBuffer(
   frame.pixel_height = 1;
   frame.fourcc = static_cast<uint32>(cricket::FOURCC_NV12);
   frame.time_stamp = currentTime;
-  frame.elapsed_time = currentTime - _startTime;
   frame.data = yPlaneAddress;
   frame.data_size = frameSize;