Remove calls to deprecated MessageLoop methods in ios.

ios/chrome/browser/browser_state/test_chrome_browser_state.mm

Index: ios/chrome/browser/browser_state/test_chrome_browser_state.mm
diff --git a/ios/chrome/browser/browser_state/test_chrome_browser_state.mm b/ios/chrome/browser/browser_state/test_chrome_browser_state.mm
index 1e5dd33a4fce4a0221580300ac34128f77e84d71..de4ba06c46c1a8cc0fa234e0c91e30dba036a949 100644
--- a/ios/chrome/browser/browser_state/test_chrome_browser_state.mm
+++ b/ios/chrome/browser/browser_state/test_chrome_browser_state.mm
@@ -360,9 +360,10 @@ void TestChromeBrowserState::DestroyHistoryService() {
   if (!history_service)
     return;
 
+  base::RunLoop run_loop;
+
   history_service->ClearCachedDataForContextID(0);
-  history_service->SetOnBackendDestroyTask(
-      base::MessageLoop::QuitWhenIdleClosure());
+  history_service->SetOnBackendDestroyTask(run_loop.QuitWhenIdleClosure());
   history_service->Shutdown();
   history_service = nullptr;
 
@@ -374,13 +375,11 @@ void TestChromeBrowserState::DestroyHistoryService() {
   // moving to the next test. Note: if this never terminates, somebody is
   // probably leaking a reference to the history backend, so it never calls
   // our destroy task.
-  base::MessageLoop::current()->Run();
+  run_loop.Run();
 
   // Make sure we don't have any event pending that could disrupt the next
   // test.
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
-      FROM_HERE, base::MessageLoop::QuitWhenIdleClosure());
-  base::MessageLoop::current()->Run();
+  base::RunLoop().RunUntilIdle();

[sdefresne, 2016/09/07 11:06:36]

Why use a second base::RunLoop() object here instead of reusing the local
variable run_loop declared above?

[fdoray, 2016/09/07 13:16:03]

A RunLoop can't be reused.

In the latest patch set, I removed this line. Since |run_loop| is quit using
QuitWhenIdleClosure, we know that the MessageLoop is idle when line 378 returns
(and hence line 382 is useless).

 }
 
 syncable_prefs::TestingPrefServiceSyncable*