Remove calls to deprecated MessageLoop methods in ios.

This CL (hopefully) removes all calls to these methods in ios:
- MessageLoop::PostTask
- MessageLoop::PostDelayedTask
- MessageLoop::DeleteSoon
- MessageLoop::ReleaseSoon
- MessageLoop::Run
- MessageLoop::RunUntilIdle

BUG=616447
R=sdefresne@chromium.org

Review-Url: https://codereview.chromium.org/2314243002
Cr-Commit-Position: refs/heads/master@{#417305}

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 +375,7 @@ 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();
-
-  // 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();
+  run_loop.Run();
 }
 
 syncable_prefs::TestingPrefServiceSyncable*

ios/web/webui/url_data_manager_ios_backend.mm

@@ -17,6 +17,7 @@
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/single_thread_task_runner.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
@@ -461,11 +462,11 @@ bool URLDataManagerIOSBackend::StartRequest(const net::URLRequest* request,
   // replies are put on the IO thread in the same order.
   base::MessageLoop* target_message_loop =
       web::WebThread::UnsafeGetMessageLoopForThread(web::WebThread::UI);
-  target_message_loop->PostTask(
+  target_message_loop->task_runner()->PostTask(
       FROM_HERE, base::Bind(&GetMimeTypeOnUI, base::RetainedRef(source), path,
                             job->weak_factory_.GetWeakPtr()));
 
-  target_message_loop->PostTask(
+  target_message_loop->task_runner()->PostTask(
       FROM_HERE, base::Bind(&URLDataManagerIOSBackend::CallStartRequest,
                             make_scoped_refptr(source), path, request_id));
   return true;