https://bugs.webkit.org/show_bug.cgi?id=116817

Reviewed by Eric Carlson.

Source/WebCore:

Add appropriate behavior for preload="metadata". Delay enabling download buffering
until playback is started in this case. This behavior fits with the standard quite
well and this is the most exact match we can get (at least without adding too much
extra complexity). What matters mostly is that we can avoid loading the media
before playback but we have the first frame and the metadata.

Test: media/video-load-preload-metadata.html

* platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
(WebCore::MediaPlayerPrivateGStreamer::prepareToPlay): Set |m_preload| to |Auto|
so we will start download buffering if we did not start it yet.
(WebCore::MediaPlayerPrivateGStreamer::play): Ditto.
(MediaPlayerPrivateGStreamer::setDownloadBuffering): Only start download
buffering if |m_preload == Auto|. Also make sure we don't clear the download
flag once we started downloading because it would result in not well defined
behavior and it does not really makes sense.
(MediaPlayerPrivateGStreamer::setPreload): Set download buffering accordingly.

LayoutTests:

* media/video-load-preload-metadata.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@152391 268f45cc-cd09-0410-ab3c-d52691b4dbfc