HTMLMediaElement should fire 'progress' event before 'idle' if it was previously...

HTMLMediaElement should fire 'progress' event before 'idle' if it was previously loading
https://bugs.webkit.org/show_bug.cgi?id=76568

Reviewed by Eric Carlson.

This fires a progress event when going from a non-empty state to idle,
for the same reason that a progress event is fired when going from a
non-idle state to loaded. Also consolidated logic in a single helper method.

No new tests because the decision of if/when a user agent sets the network state
to idle is up to the user agent in this scenario.

* html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::setNetworkState):
(WebCore::HTMLMediaElement::changeNetworkStateFromLoadingToIdle):
* html/HTMLMediaElement.h:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105365 268f45cc-cd09-0410-ab3c-d52691b4dbfc