src/vs/workbench/services/environment/browser/environmentService.ts/BrowserWorkbenchEnvironmentService/isExtensionDevelopment
class BrowserWorkbenchEnvironmentService:	get isExtensionDevelopment(): boolean {
		if (!this.extensionHostDebugEnvironment) {
			this.extensionHostDebugEnvironment = this.resolveExtensionHostDebugEnvironment();
		}

		return this.extensionHostDebugEnvironment.isExtensionDevelopment;
	}