Making flaky test consistent with non-flaky tests

The flake is due to click happening before layout meaning the click
message happens before the onLoad message. This switches the order
of a WaitForLayout and RunUntilIdle pair of calls.

Bug: None
Change-Id: Icc52d88317521ac584d92576be41d9ebfea9a638
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611916
Commit-Queue: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659636}

chrome/browser/navigation_predictor/navigation_predictor_browsertest.cc

@@ -318,12 +318,12 @@ IN_PROC_BROWSER_TEST_F(
 
   const GURL& url = GetTestURL("/page_with_same_host_anchor_element.html");
   ui_test_utils::NavigateToURL(browser(), url);
-  base::RunLoop().RunUntilIdle();
+  WaitForLayout(&histogram_tester);
 
   EXPECT_TRUE(content::ExecuteScript(
       browser()->tab_strip_model()->GetActiveWebContents(),
       "document.getElementById('google').click();"));
-  WaitForLayout(&histogram_tester);
+  base::RunLoop().RunUntilIdle();
 
   histogram_tester.ExpectUniqueSample(
       "AnchorElementMetrics.Visible.NumberOfAnchorElements", 2, 1);