Media engine should not be told to prepare for playback if media loading is not allowed

Media engine should not be told to prepare for playback if media loading is not allowed
https://bugs.webkit.org/show_bug.cgi?id=83620

Reviewed by Dan Bernstein.

Source/WebCore:

Test: media/video-load-require-user-gesture.html

* html/HTMLMediaElement.cpp:
(WebCore::HTMLMediaElement::load): Early return if user gesture requirement is not met.

* testing/InternalSettings.cpp:
(WebCore::InternalSettings::setMediaPlaybackRequiresUserGesture): Moved the method here from
    Internals to be with the rest of the Internals methods that expose preferences.
* testing/InternalSettings.h:
* testing/InternalSettings.idl:

* testing/Internals.cpp: Moved setMediaPlaybackRequiresUserGesture to InternalSettings.
* testing/Internals.h:
* testing/Internals.idl:

LayoutTests:

* media/video-load-require-user-gesture-expected.txt: Added.
* media/video-load-require-user-gesture.html: Added.
* media/video-play-require-user-gesture.html: Update for move of setMediaPlaybackRequiresUserGesture
    from window.internals to window.internals.settings.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@114021 268f45cc-cd09-0410-ab3c-d52691b4dbfc