Added 'Cancel' drop target from all apps and widget picker.

- Reuse DeleteDropTarget since it's the same effect, but with "Cancel"
  instead of "Remove" if supportsDeleteDropTarget() returns false.
- Rename related strings (but not their values)

Bug: 24104015
Bug: 24099531
Change-Id: Ia9fbcaa17bb17f7aa31df1f830298da01544c178
diff --git a/src/com/android/launcher3/SearchDropTargetBar.java b/src/com/android/launcher3/SearchDropTargetBar.java
index 878a474..9bda8b8 100644
--- a/src/com/android/launcher3/SearchDropTargetBar.java
+++ b/src/com/android/launcher3/SearchDropTargetBar.java
@@ -103,12 +103,12 @@
     }
 
     @Override
-    public void showDropTarget() {
+    public void showDropTargets() {
         animateToState(State.DROP_TARGET, DEFAULT_DRAG_FADE_DURATION);
     }
 
     @Override
-    public void hideDropTarget() {
+    public void hideDropTargets() {
         animateToState(State.SEARCH_BAR, DEFAULT_DRAG_FADE_DURATION);
     }