Tab Search: Flaky test fix

Modified `Verify ShowUI()` test to avoid timing issues that can cause
the test to flake and re-enabled it.

Move the listenOnce/showUI logic to the ready() function of the
component.

Bug: 1148061
Change-Id: I1a583dcc1ba531b39e8f92a5f9b9faf4fcfc18e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2538150Reviewed-by: Thomas Lukaszewicz <tluk@chromium.org>
Commit-Queue: Roman Arora <romanarora@chromium.org>
Cr-Commit-Position: refs/heads/master@{#832026}

chrome/browser/resources/tab_search/app.js

@@ -134,6 +134,22 @@ export class TabSearchAppElement extends PolymerElement {
         callbackRouter.tabUpdated.addListener(tab => this.onTabUpdated_(tab)),
         callbackRouter.tabsRemoved.addListener(
             tabIds => this.onTabsRemoved_(tabIds)));
+
+    // The infinite-list only triggers a dom-change event after it is ready
+    // and observes a change on the list items.
+    listenOnce(this.$.tabsList, 'dom-change', () => {
+      // Push showUI() to the event loop to allow reflow to occur following
+      // the DOM update.
+      setTimeout(() => {
+        this.apiProxy_.showUI();
+
+        // Record the first time it takes for the initial list of tabs to
+        // render.
+        chrome.metricsPrivate.recordTime(
+            'Tabs.TabSearch.WebUI.InitialTabsRenderTime',
+            Math.round(window.performance.now()));
+      }, 0);
+    });
     this.updateTabs_();
   }
 
@@ -151,20 +167,6 @@ export class TabSearchAppElement extends PolymerElement {
           'Tabs.TabSearch.WebUI.TabListDataReceived',
           Math.round(Date.now() - getTabsStartTimestamp));
 
-      // Prior to the first load |this.openTabs_| has not been set. Record the
-      // time it takes for the initial list of tabs to render.
-      if (!this.openTabs_) {
-        listenOnce(this.$.tabsList, 'dom-change', () => {
-          // Push showUI() to the event loop to allow reflow to occur following
-          // the DOM update.
-          setTimeout(() => {
-            this.apiProxy_.showUI();
-            chrome.metricsPrivate.recordTime(
-                'Tabs.TabSearch.WebUI.InitialTabsRenderTime',
-                Math.round(window.performance.now()));
-          }, 0);
-        });
-      }
       this.openTabs_ = profileTabs.windows;
     });
   }

chrome/test/data/webui/tab_search/tab_search_app_test.js

@@ -276,9 +276,10 @@ suite('TabSearchAppTest', () => {
     };
 
     await setupTest(sampleData());
+    await testProxy.whenCalled('showUI');
     await waitAfterNextRender(tabSearchApp);
 
-    // Make sure that tab data has been recieved.
+    // Make sure that tab data has been received.
     verifyTabIds(queryRows(), [ 1, 5, 6, 2, 3, 4 ]);
 
     // Ensure that |chrome.metricsPrivate.recordTime()| has been called
@@ -359,21 +360,16 @@ suite('TabSearchAppTest', () => {
         });
   });
 
-  /** TODO(crbug.com/1148061) Investigate/Fix flaky test. */
-  // Casting to avoid inexistent skip() function closure validation error.
-  /** @type {!Object} */
-  (test).skip('Verify showUI() is called correctly', async () => {
-    assertEquals(0, testProxy.getCallCount('showUI'));
-
+  test('Verify showUI() is called correctly', async () => {
     await setupTest(sampleData());
     await waitAfterNextRender(tabSearchApp);
 
     // Make sure that tab data has been received.
     verifyTabIds(queryRows(), [ 1, 5, 6, 2, 3, 4 ]);
 
-    // Ensure that showUI() has been called once after initial data has been
+    // Ensure that showUI() has been called after the initial data has been
     // rendered.
-    assertEquals(1, testProxy.getCallCount('showUI'));
+    await testProxy.whenCalled('showUI');
 
     // Force a change to filtered tab data that would result in a
     // re-render.