[Setup] Theme ChooseLockGeneric for setup wizard

This is step one of theming the set-up lock screen flow to match the
setup wizard theme. This shows the general approach of creating a
subclass of both the activity and fragment and overriding methods to
achieve the desired behavior for setup.

ag/594000 is a much more comprehensive change for what the final
change will look like.

Bug: 18482708
Change-Id: Idff34937f39f46a0c488df2cae4c46155b80cab7

src/com/android/settings/ChooseLockGeneric.java

@@ -19,6 +19,7 @@ package com.android.settings;
 import android.accessibilityservice.AccessibilityServiceInfo;
 import android.app.Activity;
 import android.app.ActivityManagerNative;
+import android.app.Fragment;
 import android.app.PendingIntent;
 import android.app.admin.DevicePolicyManager;
 import android.content.Context;
@@ -50,7 +51,7 @@ public class ChooseLockGeneric extends SettingsActivity {
     @Override
     public Intent getIntent() {
         Intent modIntent = new Intent(super.getIntent());
-        modIntent.putExtra(EXTRA_SHOW_FRAGMENT, ChooseLockGenericFragment.class.getName());
+        modIntent.putExtra(EXTRA_SHOW_FRAGMENT, getFragmentClass().getName());
         return modIntent;
     }
 
@@ -60,6 +61,10 @@ public class ChooseLockGeneric extends SettingsActivity {
         return false;
     }
 
+    /* package */ Class<? extends Fragment> getFragmentClass() {
+        return ChooseLockGenericFragment.class;
+    }
+
     public static class InternalActivity extends ChooseLockGeneric {
     }