Initiate Hotseat drag from long pressing corresponding Taskbar item

When you long press on the taskbar hotseat item, the following happens:
- We start a system drag and drop with an invisible drag shadow
- We create a new DragOptions with the simulatedDndStartPoint set to the
  drag down position, and tell Launcher to use that for the next drag
- We perform a long click on the equivalent Hotseat item in Launcher
- We pass the drag events of that operation to Launcher's DragController

This allows Launcher to handle the entire drag operation, including the
pre-drag (with popup), and taskbar already hides when the drag starts.

Test: Long press items in taskbar hotseat, able to drag them to workspace

Bug: 179886115
Bug: 171917176
Change-Id: I576b80cb1bd0225cdc91cf7689fdee0481265109
diff --git a/src/com/android/launcher3/Hotseat.java b/src/com/android/launcher3/Hotseat.java
index ebaacb6..b2112ad 100644
--- a/src/com/android/launcher3/Hotseat.java
+++ b/src/com/android/launcher3/Hotseat.java
@@ -21,6 +21,7 @@
 import android.util.AttributeSet;
 import android.view.Gravity;
 import android.view.MotionEvent;
+import android.view.View;
 import android.view.ViewDebug;
 import android.view.ViewGroup;
 import android.widget.FrameLayout;
@@ -166,4 +167,11 @@
     protected void showInlineQsb() {
         //Does nothing
     }
+
+    /**
+     * Returns the first View for which the given itemOperator returns true, or null.
+     */
+    public View getFirstItemMatch(Workspace.ItemOperator itemOperator) {
+        return mWorkspace.getFirstMatch(new CellLayout[] { this }, itemOperator);
+    }
 }