Add support for HTMLMediaElement::getStartDate()

Source/core/html/HTMLMediaElement.h

Index: Source/core/html/HTMLMediaElement.h
diff --git a/Source/core/html/HTMLMediaElement.h b/Source/core/html/HTMLMediaElement.h
index 2c6e4e9d00f0e363df128d2ea4060c6a8c7b6527..e18e7dc2e530d63a7afe32348e8af7f8c58e98df 100644
--- a/Source/core/html/HTMLMediaElement.h
+++ b/Source/core/html/HTMLMediaElement.h
@@ -127,6 +127,7 @@ public:
     double currentTime() const;
     void setCurrentTime(double, ExceptionState&);
     double duration() const;
+    double getStartDate();
     bool paused() const;
     double defaultPlaybackRate() const;
     void setDefaultPlaybackRate(double);
@@ -441,6 +442,10 @@ private:
     // Cached duration to suppress duplicate events if duration unchanged.
     double m_duration;
 
+    // Holds the "timeline offset" as described in the HTML5 spec. Represents the
+    // number of seconds since January 1, 1970 or NaN if no offset is in effect.

[acolwell GONE FROM CHROMIUM, 2014/05/15 13:01:22]

s/seconds/milliseconds.

+    double m_timelineOffset;
+
     // The last time a timeupdate event was sent (wall clock).
     double m_lastTimeUpdateEventWallTime;