Move DataSource::SetPreload() to BufferedDataSource.

Move DataSource::SetPreload() to BufferedDataSource.

Preload is a concept that only applies to HTML media elements and is only implemented by BufferedDataSource. Since the preload value is known when BufferedDataSource is created by WebMediaPlayerImpl, we can remove a lot of unnecessary plumbing in the media code.

TEST=amount of data buffered (either visible on controls or via buffered attribute) is the same for each preload value (none, metadata, and auto). http://mastodon.sea/demos/preload contains a test page.

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=130004

[scherkus (not reviewing), 2012-03-27 02:52:06]

https://chromiumcodereview.appspot.com/9864022/diff/1/webkit/media/webmediapl...
File webkit/media/webmediaplayer_impl.cc (right):

https://chromiumcodereview.appspot.com/9864022/diff/1/webkit/media/webmediapl...
webkit/media/webmediaplayer_impl.cc:377: // XXX: Why do I need to use
webkit_media:: prefix? clang complains!
note: I'm investigating this

[scherkus (not reviewing), 2012-03-27 02:52:23]

note this CL depends on https://chromiumcodereview.appspot.com/9836102/

[scherkus (not reviewing), 2012-03-30 20:12:09]

ping vrk!

[vrk (LEFT CHROMIUM), 2012-03-30 23:34:49]

LGTM

So much nicer!! Thanks scherkus!