Show notification icon in place of "1" in badge.

- When notifications update, add the NotificationInfo to the
  BadgeInfo if there is only one for an app. BadgeRenderer
  will use the NotificationInfo to get the icon to draw.
- When retrieving the icon from the NotificationInfo, we draw
  it into a shader (similar to MaskableIconDrawable), which is
  rendered by BadgeRenderer.
- For now, we only use the notification icon if it is large.

Bug: 34839959
Bug: 32410600
Bug: 33553066
Change-Id: I31851804008dd15bab75d2759441187830c3265e