Enable round-tripping and updating of SourceBuffer timestamp offset

Source/modules/mediasource/SourceBuffer.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 520 matching lines @@
     // Step 2 doesn't apply since we run Step 1 synchronously here.
     size_t appendSize = m_pendingAppendData.size();
     if (!appendSize) {
         // Resize buffer for 0 byte appends so we always have a valid pointer.
         // We need to convey all appends, even 0 byte ones to |m_webSourceBuffer|
         // so that it can clear its end of stream state if necessary.
         m_pendingAppendData.resize(1);
     }
     m_webSourceBuffer->append(m_pendingAppendData.data(), appendSize);
 
+    // Update our cached |m_timestampOffset| since the implementation may change
+    // it during append() processing.
+    m_timestampOffset = m_webSourceBuffer->getTimestampOffset();

[acolwell GONE FROM CHROMIUM, 2014/02/25 17:50:57]

See my comments in the Chromium-side changes. I think this should be a
conditional update and getTimestampOffset() should be something along the lines
of getTimestampOffsetUpdate(). m_timestampOffset should only be updated if
getTimestampOffsetUpdate() returns something other than NaN.

[wolenetz, 2014/02/25 20:33:32]

Done.

+
     // 3. Set the updating attribute to false.
     m_updating = false;
     m_pendingAppendData.clear();
 
     // 4. Queue a task to fire a simple event named update at this SourceBuffer object.
     scheduleEvent(EventTypeNames::update);
 
     // 5. Queue a task to fire a simple event named updateend at this SourceBuffer object.
     scheduleEvent(EventTypeNames::updateend);
     TRACE_EVENT_ASYNC_END0("media", "SourceBuffer::appendBuffer", this);
@@ skipping 134 matching lines @@
     WTF_LOG(Media, "SourceBuffer::didStartLoading() %p", this);
 }
 
 void SourceBuffer::didReceiveDataForClient(const char* data, unsigned dataLength)
 {
     WTF_LOG(Media, "SourceBuffer::didReceiveDataForClient(%d) %p", dataLength, this);
     ASSERT(m_updating);
     ASSERT(m_loader);
 
     m_webSourceBuffer->append(reinterpret_cast<const unsigned char*>(data), dataLength);
+
+    // Update our cached |m_timestampOffset| since the implementation may change
+    // it during append() processing.
+    m_timestampOffset = m_webSourceBuffer->getTimestampOffset();

[acolwell GONE FROM CHROMIUM, 2014/02/25 17:50:57]

ditto. Perhaps put the update logic in a updateTimestampOffsetIfNecessary()
helper.

[wolenetz, 2014/02/25 20:33:32]

Done.

 }
 
 void SourceBuffer::didFinishLoading()
 {
     WTF_LOG(Media, "SourceBuffer::didFinishLoading() %p", this);
     appendStreamDone(true);
 }
 
 void SourceBuffer::didFail(FileError::ErrorCode errorCode)
 {
     WTF_LOG(Media, "SourceBuffer::didFail(%d) %p", errorCode, this);
     appendStreamDone(false);
 }
 
 void SourceBuffer::trace(Visitor* visitor)
 {
     visitor->trace(m_source);
 }
 
 } // namespace WebCore