Flush TaskScheduler in ProfileBrowserTest.*.

chrome/browser/profiles/profile_browsertest.cc

Index: chrome/browser/profiles/profile_browsertest.cc
diff --git a/chrome/browser/profiles/profile_browsertest.cc b/chrome/browser/profiles/profile_browsertest.cc
index 0836d8323d5a70cea15b3c1fb6eb1d6d22e5ded4..2c689385873559b17e91004f91defeaf79c0f905 100644
--- a/chrome/browser/profiles/profile_browsertest.cc
+++ b/chrome/browser/profiles/profile_browsertest.cc
@@ -18,6 +18,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/sequenced_task_runner.h"
 #include "base/synchronization/waitable_event.h"
+#include "base/task_scheduler/task_scheduler.h"
 #include "base/values.h"
 #include "base/version.h"
 #include "build/build_config.h"
@@ -152,6 +153,10 @@ void SpinThreads() {
   content::RunAllPendingInMessageLoop();
   content::RunAllPendingInMessageLoop(content::BrowserThread::DB);
   content::RunAllPendingInMessageLoop(content::BrowserThread::FILE);
+
+  // This prevents HistoryBackend from accessing its databases after the
+  // directory that contains them has been deleted.
+  base::TaskScheduler::GetInstance()->FlushForTesting();
 }
 
 // Sends an HttpResponse for requests for "/" that result in sending an HPKP