Browser: inkognito mode is not supported in 4.4

http://jira.omnirom.org/browse/OMNI-59

What the hell google!
https://github.com/omnirom/android_frameworks_webview/blob/android-4.4/chromium/java/com/android/webview/chromium/WebViewChromium.java#L202

Change-Id: Ie046df74499e7cfc5dbd2d34c8706df860e8304d