Chrome-side implementation of media source timestamp offset

media/webm/webm_cluster_parser.cc

Index: media/webm/webm_cluster_parser.cc
diff --git a/media/webm/webm_cluster_parser.cc b/media/webm/webm_cluster_parser.cc
index c5a2fdc598237800758df3d8e88acdefc914cff4..64069a9c075889df7ad3fbc8ff15fce5676b7d2b 100644
--- a/media/webm/webm_cluster_parser.cc
+++ b/media/webm/webm_cluster_parser.cc
@@ -75,6 +75,14 @@ int WebMClusterParser::Parse(const uint8* buf, int size) {
   return result;
 }
 
+void WebMClusterParser::SetTimestampOffset(base::TimeDelta offset) {
+  timestamp_offset_ = offset;
+}
+
+void WebMClusterParser::ClearTimestampOffset() {
+  SetTimestampOffset(base::TimeDelta());
+}
+
 WebMParserClient* WebMClusterParser::OnListStart(int id) {
   if (id == kWebMIdCluster) {
     cluster_timecode_ = -1;
@@ -191,7 +199,8 @@ bool WebMClusterParser::OnBlock(int track_num, int timecode,
   last_block_timecode_ = timecode;
 
   base::TimeDelta timestamp = base::TimeDelta::FromMicroseconds(
-      (cluster_timecode_ + timecode) * timecode_multiplier_);
+      (cluster_timecode_ + timecode) * timecode_multiplier_) +
+      timestamp_offset_;
 
   // The first bit of the flags is set when the block contains only keyframes.
   // http://www.matroska.org/technical/specs/index.html