Add all permissions screen

Bug: 21268041
Change-Id: I51674ffbd252bf4585a992f8cc9e43973ce43512
diff --git a/PermissionController/proguard.flags b/PermissionController/proguard.flags
index f0a0f47..115958f 100644
--- a/PermissionController/proguard.flags
+++ b/PermissionController/proguard.flags
@@ -2,4 +2,7 @@
 # Don't warn about those in case this app is linking against an older
 # platform version.  We know about them, and they are safe.
 
+-keep class android.support.v7.preference.Preference* {
+    *;
+}
 -dontwarn android.support.v4.**