Calculate taskbar content size for edu

Using the value calculated in layout was not working because TaskbarView onLayout() was being called after TaskbarEduView onMeasure(). Now uses the same value on all orientations based on taskbar icon size.

Fixes: 252945031
Test: manual
Change-Id: Ib6914901638c82f3b3ec4c9b86f6c20e84d34d0f

quickstep/src/com/android/launcher3/taskbar/TaskbarViewController.java

@@ -193,6 +193,10 @@ public class TaskbarViewController implements TaskbarControllers.LoggableTaskbar
         return mTaskbarView.getIconLayoutBounds();
     }
 
+    public int getIconLayoutWidth() {
+        return mTaskbarView.getIconLayoutWidth();
+    }
+
     public View[] getIconViews() {
         return mTaskbarView.getIconViews();
     }