Fix the time origin of delayed MIDIOutput::send

MIDIOutput starts using Performance::timeOrigin() as the time origin of
the delayed send request, which is wrong.
As timeOrigin() is a web-exposed, it's relative to a different timing to
TimeTicks value. We should use Performance::GetTimeOrigin() instread.

Bug: 835664
Change-Id: I413ed6387351d55a72150163d09cfa2eb66bca92
Reviewed-on: https://chromium-review.googlesource.com/1025450Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Cr-Commit-Position: refs/heads/master@{#553012}

third_party/blink/renderer/modules/webmidi/midi_output.cc

@@ -79,7 +79,7 @@ base::TimeTicks GetTimeOrigin(ExecutionContext* context) {
 
   DCHECK(performance);
   return base::TimeTicks() +
-         TimeDelta::FromMillisecondsD(performance->timeOrigin());
+         TimeDelta::FromSecondsD(performance->GetTimeOrigin());
 }
 
 class MessageValidator {