src/vs/workbench/contrib/extensions/browser/extensionsViews.ts/ExtensionsViewState/onFocusChange
class ExtensionsViewState:	onFocusChange(extensions: IExtension[]): void {
		this.currentlyFocusedItems.forEach(extension => this._onBlur.fire(extension));
		this.currentlyFocusedItems = extensions;
		this.currentlyFocusedItems.forEach(extension => this._onFocus.fire(extension));
	}