Add dynamic summaries to Slices

Summary on slices will now determined by checking that
summaries in the following order are valid:
1) SliceData summary
2) Preference Controller summary
3) SliceData screen title

Valid is currently defined as:
- Not empty / null
- Not whitespace
- Not sumamry placeholder

Fixes: 71640678
Test: robotests
Change-Id: I5e699e8566ece80742d311617b7dc4e9a9bda8cf

src/com/android/settings/slices/SliceBroadcastReceiver.java

@@ -71,7 +71,7 @@ public class SliceBroadcastReceiver extends BroadcastReceiver {
             throw new IllegalStateException("No key passed to Intent for toggle controller");
         }
 
-        BasePreferenceController controller = getBasePreferenceController(context, key);
+        final BasePreferenceController controller = getPreferenceController(context, key);
 
         if (!(controller instanceof TogglePreferenceController)) {
             throw new IllegalStateException("Toggle action passed for a non-toggle key: " + key);
@@ -79,12 +79,12 @@ public class SliceBroadcastReceiver extends BroadcastReceiver {
 
         // TODO post context.getContentResolver().notifyChanged(uri, null) in the Toggle controller
         // so that it's automatically broadcast to any slice.
-        TogglePreferenceController toggleController = (TogglePreferenceController) controller;
-        boolean currentValue = toggleController.isChecked();
+        final TogglePreferenceController toggleController = (TogglePreferenceController) controller;
+        final boolean currentValue = toggleController.isChecked();
         toggleController.setChecked(!currentValue);
     }
 
-    private BasePreferenceController getBasePreferenceController(Context context, String key) {
+    private BasePreferenceController getPreferenceController(Context context, String key) {
         final SlicesDatabaseAccessor accessor = new SlicesDatabaseAccessor(context);
         final SliceData sliceData = accessor.getSliceDataFromKey(key);
         return SliceBuilderUtils.getPreferenceController(context, sliceData);