In iOS 8 b4, as with iOS 7.0 but not iOS 7.1, the two large invisible touch regions at the top and bottom of the landscape display more often than not bring up the browser UI, overlap the game content, and don't send the touch to the game. This means games designed for other browsers with fixed viewports - including iOS 7.1! - often become unplayable, since they may have menu options or crucial gameplay buttons in those areas. Some games also really need the extra viewport space given by minimal-ui to provide a decent experience. The change in iOS 7.1 was really nice and basically fixed the worst problems with iOS 7.0, but iOS 8 b4 has reverted back to the bad old days. The ideal solution is to support the fullscreen API and support orientation lock when in fullscreen mode, like Chrome for Android (orientation lock part coming soon). Otherwise with these restrictions in place the Safari browser is more or less a write-off for publishing browser games.
This is really a Safari issue rather than a WebKit issue. You should file the bug on bugreport.apple.com. I am closing the bug because there is nothing we can do here. You should get the conversation started with the Safari engineers on how to support your use cases.