Enable round-tripping and updating of WebSourceBufferImpl timestamp offset

content/renderer/media/websourcebuffer_impl.cc

Index: content/renderer/media/websourcebuffer_impl.cc
diff --git a/content/renderer/media/websourcebuffer_impl.cc b/content/renderer/media/websourcebuffer_impl.cc
index a7d8d8a537803b4f9a2a8bdf42777af21720a5a0..b4a4503706058acf5a615dfa39df26098e9c0b2f 100644
--- a/content/renderer/media/websourcebuffer_impl.cc
+++ b/content/renderer/media/websourcebuffer_impl.cc
@@ -72,9 +72,11 @@ void WebSourceBufferImpl::remove(double start, double end) {
 }
 
 bool WebSourceBufferImpl::setTimestampOffset(double offset) {
-  base::TimeDelta time_offset = base::TimeDelta::FromMicroseconds(
-      offset * base::Time::kMicrosecondsPerSecond);
-  return demuxer_->SetTimestampOffset(id_, time_offset);
+  return demuxer_->SetTimestampOffset(id_, offset);
+}
+
+double WebSourceBufferImpl::getTimestampOffset() {
+  return demuxer_->GetTimestampOffset(id_);
 }
 
 void WebSourceBufferImpl::setAppendWindowStart(double start) {