shadows/framework/src/main/java/org/robolectric/shadows/ShadowDisplay.java
@Deprecated
  @Implementation
  protected int getDisplayId() {
    return displayId == null
        ? directlyOn(realObject, Display.class).getDisplayId()
        : displayId;
  }
@Deprecated
  @Implementation
  protected int getDisplayId() {
    return displayId == null
        ? directlyOn(realObject, Display.class).getDisplayId()
        : displayId;
  }
If {@link #setDisplayId(int)} has been called, this method will return the specified value.

@deprecated This behavior is deprecated and will be removed in Robolectric 3.7.