Exclude invalid timestamp data for PresentationTimeRecorder

It turns out that timestamp data for the PresentationFeedback
is not set on some board, which makes the delta value to be
negative.

This should be errors and should not report data points.

Bug: b/165951963
Test: tast.ui.LauncherDragPerf on lazor to see failures
Change-Id: Ie04e57d173601a827d581eb51918a2471c82fc94
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2373262
Commit-Queue: Jun Mukai <mukai@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801434}

ash/public/cpp/presentation_time_recorder.cc

@@ -143,6 +143,7 @@ bool PresentationTimeRecorder::PresentationTimeRecorderInternal::RequestNext() {
   if (report_immediately_for_test) {
     state_ = COMMITTED;
     gfx::PresentationFeedback feedback;
+    feedback.timestamp = now;
     OnPresented(request_count_++, now, feedback);
     return true;
   }
@@ -170,7 +171,20 @@ void PresentationTimeRecorder::PresentationTimeRecorderInternal::OnPresented(
                  << ", flags=" << ToFlagString(feedback.flags);
     return;
   }
+  if (feedback.timestamp.is_null()) {
+    // TODO(b/165951963): ideally feedback.timestamp should not be null.
+    // Consider replacing this by DCHECK or CHECK.
+    LOG(ERROR) << "Invalid feedback timestamp (" << count << "):"
+               << " timestamp is not set";
+    return;
+  }
   const base::TimeDelta delta = feedback.timestamp - requested_time;
+  if (delta.InMilliseconds() < 0) {
+    LOG(ERROR) << "Invalid timestamp for presentation feedback (" << count
+               << "): requested_time=" << requested_time
+               << " feedback.timestamp=" << feedback.timestamp;
+    return;
+  }
   if (delta.InMilliseconds() > max_latency_ms_)
     max_latency_ms_ = delta.InMilliseconds();