Enable round-tripping and updating of SourceBuffer timestamp offset

public/platform/WebSourceBuffer.h

Index: public/platform/WebSourceBuffer.h
diff --git a/public/platform/WebSourceBuffer.h b/public/platform/WebSourceBuffer.h
index e789648be8f95d62073d2a76d7bdaf74fbe6a0c4..0f026c856a963b00db43a1ee2ab0642e3e24005e 100644
--- a/public/platform/WebSourceBuffer.h
+++ b/public/platform/WebSourceBuffer.h
@@ -46,6 +46,18 @@ public:
     virtual bool setMode(AppendMode) = 0;
     virtual WebTimeRanges buffered() = 0;
     virtual void append(const unsigned char* data, unsigned length) = 0;
+
+    // If the append does not update the source buffer's timestamp offset,
+    // returns false and |*newTimestampOffset| is unchanged.
+    // Otherwise, returns true and |*newTimestampOffset| contains the updated offset.
+    // FIXME: Remove both the void append(...) and this method's default implementation once
+    // the Chromium implementation of this signature has landed. See http://crbug.com/249422.

[jamesr, 2014/02/27 01:18:27]

can you just land the chromium implementation first to avoid this extra step?

it's not clear to me if the return value will remain bool after the transition

[wolenetz, 2014/02/27 01:44:56]

I was going on acolwell@'s separate suggestion to keep the chromium and blink
changes independent. The end result of landing these two will be the chromium
implementation will override the bool append() here, letting me then land
another two independent changes that get rid of the old void append in each of
Blink and Chromium.

Keeping these first two independently land-able improves chances of more rapidly
getting the later two changes landed, too.

+    virtual bool append(const unsigned char* data, unsigned length, double* newTimestampOffset)
+    {
+        append(data, length);
+        return false;
+    }
+
     virtual void abort() = 0;
     virtual void remove(double start, double end) = 0;
     virtual bool setTimestampOffset(double) = 0;