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;
	}