src/vs/editor/common/viewEvents.ts/ViewDecorationsChangedEvent/constructor
class ViewDecorationsChangedEvent:	constructor(source: IModelDecorationsChangedEvent | null) {
		if (source) {
			this.affectsMinimap = source.affectsMinimap;
			this.affectsOverviewRuler = source.affectsOverviewRuler;
		} else {
			this.affectsMinimap = true;
			this.affectsOverviewRuler = true;
		}
	}