[DO NOT MERGE] Update contextual cards display mechanism

1. Make Wi-Fi card default to collapse.
2. Support showing a default card when there's no displayable card.
3. Solve the problem of icon not showing for cached slices in card
renderer

Bug: 163288869
Fixes: 159092915
Test: manual, robotest
Change-Id: Ie8b61ad58410337334e29b7a794353b0c6a6ba8c

src/com/android/settings/homepage/contextualcards/ContextualCardLoader.java

@@ -164,6 +164,16 @@ public class ContextualCardLoader extends AsyncLoaderCompat<List<ContextualCard>
                     SettingsEnums.ACTION_CONTEXTUAL_CARD_NOT_SHOW,
                     ContextualCardLogUtils.buildCardListLog(hiddenCards));
         }
+
+        // Add a default card if no other visible cards
+        if (visibleCards.isEmpty() && maxCardCount == 1) {
+            final ContextualCard defaultCard = FeatureFactory.getFactory(mContext)
+                    .getContextualCardFeatureProvider(mContext).getDefaultContextualCard();
+            if (defaultCard != null) {
+                Log.i(TAG, "Default card: " + defaultCard.getSliceUri());
+                visibleCards.add(defaultCard);
+            }
+        }
         return visibleCards;
     }