Moving some abstract classes to interfaces, to better use java-8 features

Change-Id: I862af4931c95cbde052130d8b7d4ac3375db782f
diff --git a/src/com/android/launcher3/Launcher.java b/src/com/android/launcher3/Launcher.java
index c3c4f5e..9f16857 100644
--- a/src/com/android/launcher3/Launcher.java
+++ b/src/com/android/launcher3/Launcher.java
@@ -74,7 +74,6 @@
 import android.widget.Toast;
 
 import com.android.launcher3.DropTarget.DragObject;
-import com.android.launcher3.Workspace.ItemOperator;
 import com.android.launcher3.accessibility.LauncherAccessibilityDelegate;
 import com.android.launcher3.allapps.AllAppsContainerView;
 import com.android.launcher3.allapps.AllAppsTransitionController;
@@ -1052,12 +1051,7 @@
     }
 
     public FolderIcon findFolderIcon(final long folderIconId) {
-        return (FolderIcon) mWorkspace.getFirstMatch(new ItemOperator() {
-            @Override
-            public boolean evaluate(ItemInfo info, View view) {
-                return info != null && info.id == folderIconId;
-            }
-        });
+        return (FolderIcon) mWorkspace.getHomescreenIconByItemId(folderIconId);
     }
 
     /**