[gstreamer] MediaPlayerPrivateGStreamer should take ownership of the playbin
https://bugs.webkit.org/show_bug.cgi?id=107445

Reviewed by Philippe Normand.

In gstreamer 1.0, gst_element_factory_make() now returns a floating reference.
MediaPlayerPrivateGStreamer calls gst_element_factory_make() to create the
playbin object but does not take ownership of the object. As a consequence,
the object keeps floating until it is unref'd in the
MediaPlayerPrivateGStreamer destructor.

This patch uses a GRefPtr<GstElement> to store the playbin object and only
adopt the object returned by gst_element_factory_make() if gstreamer 0.10
is used. When gstreamer 1.0 is used, the returned object will not be adopted,
which will remove the floating reference. This way, we ensure that the
playbin object is owned by MediaPlayerPrivateGStreamer.

No new tests, no behavior change for layout tests.

* platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
(WebCore::MediaPlayerPrivateGStreamer::MediaPlayerPrivateGStreamer):
(WebCore::MediaPlayerPrivateGStreamer::~MediaPlayerPrivateGStreamer):
(WebCore::MediaPlayerPrivateGStreamer::load):
(WebCore::MediaPlayerPrivateGStreamer::playbackPosition):
(WebCore::MediaPlayerPrivateGStreamer::changePipelineState):
(WebCore::MediaPlayerPrivateGStreamer::duration):
(WebCore::MediaPlayerPrivateGStreamer::seek):
(WebCore::MediaPlayerPrivateGStreamer::paused):
(WebCore::MediaPlayerPrivateGStreamer::notifyPlayerOfVideo):
(WebCore::MediaPlayerPrivateGStreamer::notifyPlayerOfAudio):
(WebCore::MediaPlayerPrivateGStreamer::setVolume):
(WebCore::MediaPlayerPrivateGStreamer::notifyPlayerOfVolumeChange):
(WebCore::MediaPlayerPrivateGStreamer::setRate):
(WebCore::MediaPlayerPrivateGStreamer::buffered):
(WebCore::MediaPlayerPrivateGStreamer::handleMessage):
(WebCore::MediaPlayerPrivateGStreamer::fillTimerFired):
* platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.h:
(MediaPlayerPrivateGStreamer):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140414 268f45cc-cd09-0410-ab3c-d52691b4dbfc