EME: MediaPlayer::keyNeede() should return a bool indicating whether an event listener was triggered.
https://bugs.webkit.org/show_bug.cgi?id=109701

Reviewed by Eric Carlson.

Clients of MediaPlayer may need to do cleanup if calling keyNeeded()
results in no event listener being triggered. Return a bool (like the
v1 equivalent keyNeeded method) to indicate this.

* html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::mediaPlayerKeyNeeded):
* html/HTMLMediaElement.h:
* platform/graphics/MediaPlayer.cpp:
(WebCore::MediaPlayer::keyNeeded):
* platform/graphics/MediaPlayer.h:
(WebCore::MediaPlayerClient::mediaPlayerKeyNeeded):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142819 268f45cc-cd09-0410-ab3c-d52691b4dbfc