Fixe some stuff.

Addresses these bugs:

3061847 - With no headers, PreferenceActivity crashes
2888426 - minor typo in DevicePolicyManagerService.ActiveAdmin.writeToXml()
3159155 - IllegalStateException:"Can not perform this action after
    onSaveInstanceState" while dismissing a DialogFragment
3155995 - PopupWindow.showAtLocation does not respect LayoutParams

Also tweak the new fragment APIs to use abstract classes instead of
interfaces as base classes.

Change-Id: I9c0b4337fe0e304b737b5f7c2762762372bb3020

services/java/com/android/server/DevicePolicyManagerService.java

@@ -175,7 +175,7 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
                     out.endTag(null, "min-password-nonletter");
                 }
             }
-            if (maximumTimeToUnlock != DevicePolicyManager.PASSWORD_QUALITY_UNSPECIFIED) {
+            if (maximumTimeToUnlock != 0) {
                 out.startTag(null, "max-time-to-unlock");
                 out.attribute(null, "value", Long.toString(maximumTimeToUnlock));
                 out.endTag(null, "max-time-to-unlock");