Enabling accessible drag and drop

-> Using the context menu, and a new two stage system, this allows
   users to curate icons and widgets on the workspace
-> Move icons / widgets to any empty cell on any existing screen, or
   create a new screen (appended to the right, as with regular drag
   and drop)
-> Move icons into existing folders
-> Create folders by moving an icon onto another icon
-> Also added confirmations for these and some existing accessibility actions

Limitations:
-> Currently, no support for drag and drop in folders
-> Considering moving the drag view so it doesn't occlude any
   content (in particular, when user changes pages)
-> In this mode, accessibility framework seems to have
   problems with the next / prev operations

Bug: 18482913

Change-Id: I19b0be9dc8bfa766d430408c8ad9303c716b89b2

src/com/android/launcher3/SearchDropTargetBar.java

@@ -197,6 +197,10 @@ public class SearchDropTargetBar extends FrameLayout implements DragController.D
      */
     @Override
     public void onDragStart(DragSource source, Object info, int dragAction) {
+        showDeleteTarget();
+    }
+
+    public void showDeleteTarget() {
         // Animate out the QSB search bar, and animate in the drop target bar
         prepareStartAnimation(mDropTargetBar);
         mDropTargetBarAnim.start();
@@ -206,6 +210,16 @@ public class SearchDropTargetBar extends FrameLayout implements DragController.D
         }
     }
 
+    public void hideDeleteTarget() {
+        // Restore the QSB search bar, and animate out the drop target bar
+        prepareStartAnimation(mDropTargetBar);
+        mDropTargetBarAnim.reverse();
+        if (!mIsSearchBarHidden) {
+            prepareStartAnimation(mQSBSearchBar);
+            mQSBSearchBarAnim.reverse();
+        }
+    }
+
     public void deferOnDragEnd() {
         mDeferOnDragEnd = true;
     }
@@ -213,13 +227,7 @@ public class SearchDropTargetBar extends FrameLayout implements DragController.D
     @Override
     public void onDragEnd() {
         if (!mDeferOnDragEnd) {
-            // Restore the QSB search bar, and animate out the drop target bar
-            prepareStartAnimation(mDropTargetBar);
-            mDropTargetBarAnim.reverse();
-            if (!mIsSearchBarHidden) {
-                prepareStartAnimation(mQSBSearchBar);
-                mQSBSearchBarAnim.reverse();
-            }
+            hideDeleteTarget();
         } else {
             mDeferOnDragEnd = false;
         }