src/vs/workbench/contrib/webview/browser/webviewElement.ts/WebviewElement/_initElement
class WebviewElement:	private _initElement(encodedWebviewOrigin: string, extension: WebviewExtensionDescription | undefined, options: WebviewOptions) {
		// The extensionId and purpose in the URL are used for filtering in js-debug:
		const params: { [key: string]: string } = {
			id: this.id,
			origin: this.origin,
			swVersion: String(this._expectedServiceWorkerVersion),
			extensionId: extension?.id.value ?? '',
			platform: this.platform,
			'vscode-resource-base-authority': webviewRootResourceAuthority,
			parentOrigin: window.origin,
		};

		if (this._environmentService.remoteAuthority) {
			params.remoteAuthority = this._environmentService.remoteAuthority;
		}

		if (options.purpose) {
			params.purpose = options.purpose;
		}

		COI.addSearchParam(params, true, true);

		const queryString = new URLSearchParams(params).toString();

		// Workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=1754872
		const fileName = isFirefox ? 'index-no-csp.html' : 'index.html';

		this.element!.setAttribute('src', `${this.webviewContentEndpoint(encodedWebviewOrigin)}/${fileName}?${queryString}`);
	}