Remove state from shared.js, move to cache.js.

lib/cache.js

@@ -0,0 +1,24 @@
+// @ts-check
+
+"use strict";
+
+let lineMetadata = null;
+module.exports.lineMetadata = (value) => {
+  if (value) {
+    lineMetadata = value;
+  }
+  return lineMetadata;
+};
+
+let flattenedLists = null;
+module.exports.flattenedLists = (value) => {
+  if (value) {
+    flattenedLists = value;
+  }
+  return flattenedLists;
+};
+
+module.exports.clear = () => {
+  lineMetadata = null;
+  flattenedLists = null;
+};