Add processing time to VideoFrame

Bug: chromium:1011581
Change-Id: Icd675cb98b8b5052933b9a8eebe718be94c2fef2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/166162
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30281}

modules/video_coding/video_receiver2.cc

@@ -91,7 +91,7 @@ int32_t VideoReceiver2::Decode(const VCMEncodedFrame* frame) {
   if (decoder == nullptr) {
     return VCM_NO_CODEC_REGISTERED;
   }
-  return decoder->Decode(*frame, clock_->TimeInMilliseconds());
+  return decoder->Decode(*frame, clock_->CurrentTime());
 }
 
 // Register possible receive codecs, can be called multiple times