Fragmentize "Factory reset" setting screen.

Split the screen into 2 fragments.

Bug: 3148480
diff --git a/proguard.flags b/proguard.flags
index 457972c..7cd46e7 100644
--- a/proguard.flags
+++ b/proguard.flags
@@ -7,3 +7,6 @@
 -keep class com.android.settings.bluetooth.*
 -keep class com.android.settings.applications.*
 -keep class com.android.settings.inputmethod.*
+-keep class com.android.settings.MasterClear
+-keep class com.android.settings.MasterClearConfirm
+