Update virtual display size before turning it on.

When a bubble is expanded, a virtual display turns on, an activity for
the bubble is resumed, and the activity draws contents on the virtual
display. The system waits until the contents is drawn, then shows the
contents in the bubble.

However, if size of the virtual display is changed after resuming the
activity, an app transition initiated by the activity is canceled, and
this sequence gets stuck. As a result, contents in the bubble is never
displayed.

Test: Manual.
Bug: 158675422
Change-Id: I3ba0805fd09f4dee36dae6a236b5b6fc7983e06b