[Sync] Try to fix race conditions in CookieJarMismatch.

chrome/browser/sync/test/integration/single_client_sessions_sync_test.cc

Index: chrome/browser/sync/test/integration/single_client_sessions_sync_test.cc
diff --git a/chrome/browser/sync/test/integration/single_client_sessions_sync_test.cc b/chrome/browser/sync/test/integration/single_client_sessions_sync_test.cc
index 92be5ac0857c7914241041c20d3e04922c918960..6003ec8a0ff4d03079a1e96f92b406997d357fc4 100644
--- a/chrome/browser/sync/test/integration/single_client_sessions_sync_test.cc
+++ b/chrome/browser/sync/test/integration/single_client_sessions_sync_test.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/macros.h"
+#include "base/run_loop.h"
 #include "base/test/histogram_tester.h"
 #include "chrome/browser/sessions/session_service.h"
 #include "chrome/browser/sync/test/integration/profile_sync_service_harness.h"
@@ -324,7 +325,7 @@ IN_PROC_BROWSER_TEST_F(SingleClientSessionsSyncTest, TabMovedToOtherWindow) {
 }
 
 // crbug.com/689662
-#if defined(OS_CHROMEOS) || defined(OS_WIN)
+#if defined(OS_CHROMEOS)
 #define MAYBE_CookieJarMismatch DISABLED_CookieJarMismatch
 #else
 #define MAYBE_CookieJarMismatch CookieJarMismatch
@@ -351,25 +352,32 @@ IN_PROC_BROWSER_TEST_F(SingleClientSessionsSyncTest, MAYBE_CookieJarMismatch) {
     ASSERT_TRUE(GetFakeServer()->GetLastCommitMessage(&message));
     ASSERT_TRUE(message.commit().config_params().cookie_jar_mismatch());
 
-    // It is possible that multiple sync cycles occured during the call to
+    // It is possible that multiple sync cycles occurred during the call to
     // OpenTab, which would cause multiple identical samples.
     ExpectUniqueSampleGE(histogram_tester, "Sync.CookieJarMatchOnNavigation",
                          false, 1);
     ExpectUniqueSampleGE(histogram_tester, "Sync.CookieJarEmptyOnMismatch",
                          true, 1);
-
-    // Trigger a cookie jar change (user signing in to content area).
-    gaia::ListedAccount signed_in_account;
-    signed_in_account.id =
-        GetClient(0)->service()->signin()->GetAuthenticatedAccountId();
-    std::vector<gaia::ListedAccount> accounts;
-    std::vector<gaia::ListedAccount> signed_out_accounts;
-    accounts.push_back(signed_in_account);
-    GoogleServiceAuthError error(GoogleServiceAuthError::NONE);
-    GetClient(0)->service()->OnGaiaAccountsInCookieUpdated(
-        accounts, signed_out_accounts, error);
   }
 
+  // Trigger a cookie jar change (user signing in to content area).
+  gaia::ListedAccount signed_in_account;
+  signed_in_account.id =
+      GetClient(0)->service()->signin()->GetAuthenticatedAccountId();
+  std::vector<gaia::ListedAccount> accounts;
+  std::vector<gaia::ListedAccount> signed_out_accounts;
+  accounts.push_back(signed_in_account);
+  GoogleServiceAuthError error(GoogleServiceAuthError::NONE);
+
+  // Updating the cookie jar has to travel to the sync engine. It is possible
+  // something is already running or scheduled to run on the sync thread. We
+  // want to block here and not create the HistogramTester below until we know
+  // the cookie jar stats have been updated.
+  base::RunLoop run_loop;
+  GetClient(0)->service()->OnGaiaAccountsInCookieUpdatedWithCallback(
+      accounts, signed_out_accounts, error, run_loop.QuitClosure());
+  run_loop.Run();

[pavely, 2017/03/20 04:32:02]

Waiting for values to arrive on sync thread doesn't guarantee they will get
recorded in histogram before HistogramTester takes snapshot. What if you called
OnGaiaAccountsInCookieUpdatedWithCallback inside the block, after
HistogramTester? This will allow you to avoid wiring callback to SBHC and back.
I think you would need less strict function to verify histogram sample presence.

+
   {
     HistogramTester histogram_tester;