Make BlobEvent::timecode as a difference from the first chunk of the BlobEvent.
spec, https://w3c.github.io/mediacapture-record/#dom-blobevent-timecode, said that the timecode is time delta from the first BlobEvent of this recorder.
Here are issues and its discussion.
w3c/mediacapture-record#222
w3c/mediacapture-record#223
Bug: 40247788
Change-Id: Ic9c74299230b9839578ca317fff056e7a1b26dc6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5631009
Commit-Queue: Sunggook Chue sunggch@microsoft.com
Reviewed-by: Markus Handell handellm@google.com
Reviewed-by: Gabriel Brito gabrielbrito@microsoft.com
Cr-Commit-Position: refs/heads/main@{#1362716}