src/vs/workbench/services/extensionManagement/common/extensionManagementService.ts/ExtensionManagementService/installVSIX
class ExtensionManagementService:	protected async installVSIX(vsix: URI, server: IExtensionManagementServer, options: InstallVSIXOptions | undefined): Promise<ILocalExtension> {
		const manifest = await this.getManifest(vsix);
		if (manifest) {
			await this.checkForWorkspaceTrust(manifest);
			return server.extensionManagementService.install(vsix, options);
		}
		return Promise.reject('Unable to get the extension manifest.');
	}