Remove HTMLMediaElement::setPausedInternal()

The bits in updatePlayState() could have been inlined into stop(), but
none of it is useful:

 - isPlaying is always false because of userCancelledLoad() ->
   clearMediaPlayer(), so webMediaPlayer()->pause() is dead code.

 - refreshCachedTime() will do nothing for the same reason.

 - m_playbackProgressTimer.stop() is done by stopPeriodicTimers().

 - mediaControls()->playbackStopped() is pointless because the document
   is no longer doing layout/rendering.

Review URL: https://codereview.chromium.org/594493003

git-svn-id: svn://svn.chromium.org/blink/trunk@182422 bbb929c8-8fbe-4397-9dbb-9b2b20218538