Fix exception in Browser Settings

Bug 11302175

Need to implement isValidFragment when targeting >= KK

Change-Id: I19cc285aa237ffd9001558a9ee6adaf152acd1df
Merge tag 'android-4.4.1_r1' into kk-4.4

Android 4.4.1 Release 1

Conflicts:
	src/com/android/browser/BrowserPreferencesPage.java