Browser: Fix browser force close

Issue: Cursor was accessed by handler thread
       when it was closed. During Orientation change,
       BrowserBookmarksPage#onDestroyView is called
       which clears all the loaders [and cursors].
       Simultaneously ThreadedCursorAdapter#loadRowObject
       is getting called which then calls
       BrowserBookmarksAdapter#getRowObject
       where closed cursor is accessed and force close happens.

Fix: Synchronized cursors wrt main thread and handler thread.
     Checked mCursorAdapter for invalid conditions

CRs-Fixed: 576176
Change-Id: I9f16c2f1a55f35e8256bbf56afce3538850f9d42
Add back browser history page.

Not sure why it was removed, but it seems to work just fine.

Change-Id: I6d76928182a53ca57d080394823d35d66e0ba987
Browser: add valid missing fragments (fixes FC)

WebsiteSettingsFragment and DebugPreferencesFragment are also valid
fragments.

Change-Id: I4e945a3b9de62879afcc621fb97811e75ca53cb1
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