src/vs/workbench/browser/parts/editor/editorPart.ts/EditorPart/doSetGroupActive
class EditorPart:	private doSetGroupActive(group: IEditorGroupView): void {
		if (this._activeGroup === group) {
			return; // return if this is already the active group
		}

		const previousActiveGroup = this._activeGroup;
		this._activeGroup = group;

		// Update list of most recently active groups
		this.doUpdateMostRecentActive(group, true);

		// Mark previous one as inactive
		if (previousActiveGroup) {
			previousActiveGroup.setActive(false);
		}

		// Mark group as new active
		group.setActive(true);

		// Maximize the group if it is currently minimized
		this.doRestoreGroup(group);

		// Event
		this._onDidChangeActiveGroup.fire(group);
	}