Fixed problem with browser menu back navigation

The user was not able to use the top button in browser's
settings and about menu to navigate back to main browser
screen. This is due to incompatibility of Fragment APIs.
Added explicit code in preference activity to navigate back.

Change-Id: Ie6616a0b9a492ab07b650f0cdcd28682855e42d9
diff --git a/src/com/android/browser/AutoFillSettingsFragment.java b/src/com/android/browser/AutoFillSettingsFragment.java
index d0ca946..6bde1a2 100644
--- a/src/com/android/browser/AutoFillSettingsFragment.java
+++ b/src/com/android/browser/AutoFillSettingsFragment.java
@@ -131,6 +131,7 @@
         if (bar != null) {
             bar.setTitle(R.string.pref_general_autofill_title);
             bar.setDisplayHomeAsUpEnabled(false);
+            bar.setHomeButtonEnabled(false);
         }
     }