feat: Better At-a-Glance perceptive wallpaper colour luminance detection

src/com/android/launcher3/WorkspaceLayoutManager.java

@@ -42,6 +42,8 @@ public interface WorkspaceLayoutManager {
 
     // The is the first screen. It is always present, even if its empty.
     int FIRST_SCREEN_ID = 0;
+    // This is the second page. On two panel home it is always present, even if its empty.
+    int SECOND_SCREEN_ID = 1;
 
     /**
      * At bind time, we use the rank (screenId) to compute x and y for hotseat items.