Correct frame timestamps in VTVideoEncodeAccelerator

This CL corrects the timestamp sent with the encoded frame data from
VTVideoEncodeAccelerator. Recently, this functionality is added to the
VEA interface and we can use the frame's original capture timestamp.

BUG=350106
TEST=AppRTC loopback in Macbook Air.

Review-Url: https://codereview.chromium.org/2039423002
Cr-Commit-Position: refs/heads/master@{#398187}

media/gpu/vt_video_encode_accelerator_mac.cc

@@ -42,10 +42,15 @@ struct VTVideoEncodeAccelerator::InProgressFrameEncode {
 };
 
 struct VTVideoEncodeAccelerator::EncodeOutput {
-  EncodeOutput(VTEncodeInfoFlags info_flags, CMSampleBufferRef sbuf)
-      : info(info_flags), sample_buffer(sbuf, base::scoped_policy::RETAIN) {}
+  EncodeOutput(VTEncodeInfoFlags info_flags,
+               CMSampleBufferRef sbuf,
+               base::TimeDelta timestamp)
+      : info(info_flags),
+        sample_buffer(sbuf, base::scoped_policy::RETAIN),
+        capture_timestamp(timestamp) {}
   const VTEncodeInfoFlags info;
   const base::ScopedCFTypeRef<CMSampleBufferRef> sample_buffer;
+  const base::TimeDelta capture_timestamp;
 
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(EncodeOutput);
@@ -393,15 +398,14 @@ void VTVideoEncodeAccelerator::CompressionCallback(void* encoder_opaque,
   auto encoder = reinterpret_cast<VTVideoEncodeAccelerator*>(encoder_opaque);
   DCHECK(encoder);
 
-  // Release InProgressFrameEncode, since we don't have support to return
-  // timestamps at this point.
-  std::unique_ptr<InProgressFrameEncode> request(
+  // InProgressFrameEncode holds timestamp information of the encoded frame.
+  std::unique_ptr<InProgressFrameEncode> frame_info(
       reinterpret_cast<InProgressFrameEncode*>(request_opaque));
-  request.reset();
 
   // EncodeOutput holds onto CMSampleBufferRef when posting task between
   // threads.
-  std::unique_ptr<EncodeOutput> encode_output(new EncodeOutput(info, sbuf));
+  std::unique_ptr<EncodeOutput> encode_output(
+      new EncodeOutput(info, sbuf, frame_info->timestamp));
 
   // This method is NOT called on |encoder_thread_|, so we still need to
   // post a task back to it to do work.
@@ -446,7 +450,7 @@ void VTVideoEncodeAccelerator::ReturnBitstreamBuffer(
     client_task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&Client::BitstreamBufferReady, client_, buffer_ref->id, 0,
-                   false, base::Time::Now() - base::Time()));
+                   false, encode_output->capture_timestamp));
     return;
   }
 
@@ -470,7 +474,7 @@ void VTVideoEncodeAccelerator::ReturnBitstreamBuffer(
   client_task_runner_->PostTask(
       FROM_HERE,
       base::Bind(&Client::BitstreamBufferReady, client_, buffer_ref->id,
-                 used_buffer_size, keyframe, base::Time::Now() - base::Time()));
+                 used_buffer_size, keyframe, encode_output->capture_timestamp));
 }
 
 bool VTVideoEncodeAccelerator::ResetCompressionSession() {