Replace drainUntilIdle with a dispatch_barrier_sync for Breakpad tests

ios/chrome/test/app/chrome_test_util.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IOS_CHROME_TEST_APP_CHROME_TEST_UTIL_H_
 #define IOS_CHROME_TEST_APP_CHROME_TEST_UTIL_H_
 
 #import "base/ios/block_types.h"
 #import "ios/web/public/web_state/web_state.h"
 
@@ skipping 50 matching lines @@
 void SetBooleanUserPref(ios::ChromeBrowserState* browser_state,
                         const char* pref_name,
                         bool value);
 
 // Sets the state of using cellular network.
 void SetWWANStateTo(bool value);
 
 // Sets the state of first launch.
 void SetFirstLaunchStateTo(bool value);
 
-// Check whether metrics recording is enabled or not.
+// Checks whether metrics recording is enabled or not.
 bool IsMetricsRecordingEnabled();
 
-// Check whether metrics reporting is enabled or not.
+// Checks whether metrics reporting is enabled or not.
 bool IsMetricsReportingEnabled();
 
-// Check whether breakpad recording is enabled or not.
+// Checks whether breakpad recording is enabled or not.
 bool IsBreakpadEnabled();
 
-// Check whether breakpad reporting is enabled or not.
+// Checks whether breakpad reporting is enabled or not.
 bool IsBreakpadReportingEnabled();
 
-// Check whether this is the first launch after upgrade or not.
+// Checks whether this is the first launch after upgrade or not.
 bool IsFirstLaunchAfterUpgrade();
 
-// Simulate launching Chrome from another application.
+// Waits for Breakpad to process the queued updates.
+void WaitForBreakpadQueue();
+
+// Simulates launching Chrome from another application.
 void OpenChromeFromExternalApp(const GURL& url);
 
 }  // namespace chrome_test_util
 
 #endif  // IOS_CHROME_TEST_APP_CHROME_TEST_UTIL_H_