[wk2] Intrinsic content size should report a flexible width if the content is not wider than the minimum layout width
https://bugs.webkit.org/show_bug.cgi?id=107334
<rdar://problem/12960009>

Reviewed by Anders Carlsson.

* UIProcess/API/mac/WKView.mm:
(-[WKView _setIntrinsicContentSize:]): If the content is laid-out at or below the minimum layout width, it's flexible; otherwise, we need to inform autolayout that we require more space via our intrinsic content size.
* WebProcess/WebCoreSupport/WebFrameLoaderClient.cpp:
(WebKit::WebFrameLoaderClient::transitionToCommittedForNewPage): Allow auto-sizing to expand its width beyond the minimum if needed.
* WebProcess/WebPage/WebPage.cpp:
(WebKit::WebPage::setMinimumLayoutWidth): Allow auto-sizing to expand its width beyond the minimum if needed.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140228 268f45cc-cd09-0410-ab3c-d52691b4dbfc