Ensure that the google charts library is loaded before calling it. (#3034)

client-src/elements/chromedash-timeline-page_test.js

@@ -12,7 +12,10 @@ describe('chromedash-timeline-page', () => {
     await fixture(html`<chromedash-toast></chromedash-toast>`);
     sinon.stub(window, 'fetch');
     // hacky way to stub out google chart load method
-    window.google = {charts: {load: () => {}}};
+    window.google = {charts: {
+      load: () => {},
+      setOnLoadCallback: (f) => f(),
+    }};
   });
 
   afterEach(() => {

client-src/elements/chromedash-timeline.js

@@ -100,7 +100,7 @@ class ChromedashTimeline extends LitElement {
   }
 
   updated() {
-    this._updateTimeline();
+    window.google.charts.setOnLoadCallback(this._updateTimeline.bind(this));
   }
 
   updateSelectedBucketId(e) {