src/vs/workbench/contrib/extensions/browser/extensionsWorkbenchService.ts/Extensions/getExtensionState
class Extensions:	getExtensionState(extension: Extension): ExtensionState {
		if (extension.gallery && this.installing.some(e => !!e.gallery && areSameExtensions(e.gallery.identifier, extension.gallery!.identifier))) {
			return ExtensionState.Installing;
		}
		if (this.uninstalling.some(e => areSameExtensions(e.identifier, extension.identifier))) {
			return ExtensionState.Uninstalling;
		}
		const local = this.installed.filter(e => e === extension || (e.gallery && extension.gallery && areSameExtensions(e.gallery.identifier, extension.gallery.identifier)))[0];
		return local ? ExtensionState.Installed : ExtensionState.Uninstalled;
	}