After r161087, contentScaleFactor of WebView is synced with pageScaleFactor of WebPage. It means that WKViewGetContentScaleFactor might not be same with PageViewportController's current scale value until received PageScaleFactorDidChange.
Created attachment 220048 [details] Patch
Comment on attachment 220048 [details] Patch LGTM
Comment on attachment 220048 [details] Patch Clearing flags on attachment: 220048 Committed r161100: <http://trac.webkit.org/changeset/161100>
All reviewed patches have been landed. Closing bug.