Enable round-tripping and updating of SourceBuffer timestamp offset

Source/modules/mediasource/SourceBuffer.cpp

Index: Source/modules/mediasource/SourceBuffer.cpp
diff --git a/Source/modules/mediasource/SourceBuffer.cpp b/Source/modules/mediasource/SourceBuffer.cpp
index 64e8021bd5204ef9799a3085f9a849c9b44815d9..8a3a8acfed9b669a7f627468c76f9fcbfcfd5a77 100644
--- a/Source/modules/mediasource/SourceBuffer.cpp
+++ b/Source/modules/mediasource/SourceBuffer.cpp
@@ -538,6 +538,10 @@ void SourceBuffer::appendBufferAsyncPart()
     }
     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();
@@ -692,6 +696,10 @@ void SourceBuffer::didReceiveDataForClient(const char* data, unsigned dataLength
     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()