src/vs/workbench/services/environment/browser/environmentService.ts/BrowserWorkbenchEnvironmentService/extensionDevelopmentLocationURI
class BrowserWorkbenchEnvironmentService:	get extensionDevelopmentLocationURI(): URI[] | undefined {
		if (!this._extensionHostDebugEnvironment) {
			this._extensionHostDebugEnvironment = this.resolveExtensionHostDebugEnvironment();
		}

		return this._extensionHostDebugEnvironment.extensionDevelopmentLocationURI;
	}