Replace drainUntilIdle with a dispatch_barrier_sync for Breakpad tests

ios/chrome/browser/ui/settings/settings_egtest.mm

 // 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.
 
 #import <EarlGrey/EarlGrey.h>
 #import <UIKit/UIKit.h>
 #import <XCTest/XCTest.h>
 #include <map>
 
 #include "base/bind.h"
@@ skipping 452 matching lines @@
 }
 
 - (void)setMetricsReportingEnabled:(BOOL)reportingEnabled
                           wifiOnly:(BOOL)wifiOnly {
   chrome_test_util::SetBooleanLocalStatePref(
       metrics::prefs::kMetricsReportingEnabled, reportingEnabled);
   chrome_test_util::SetBooleanLocalStatePref(prefs::kMetricsReportingWifiOnly,
                                              wifiOnly);
   // Breakpad uses dispatch_async to update its state. Wait to get to a
   // consistent state.
-  [[GREYUIThreadExecutor sharedInstance] drainUntilIdle];
+  chrome_test_util::WaitForBreakpadQueue();
 }
 
 // Checks for a given service that it is both recording and uploading, where
 // appropriate.
 - (void)assertMetricsServiceEnabled:(MetricsServiceType)serviceType {
   switch (serviceType) {
     case kMetrics:
       GREYAssertTrue(chrome_test_util::IsMetricsRecordingEnabled(),
                      @"Metrics recording should be enabled.");
       GREYAssertTrue(chrome_test_util::IsMetricsReportingEnabled(),
@@ skipping 104 matching lines @@
   // the services, turning on and off according to the rules laid out above.
 
   // kMetricsReportingEnabled ON and kMetricsReportingWifiOnly ON.
   [self setMetricsReportingEnabled:YES wifiOnly:YES];
   // Service should be enabled.
   [self assertMetricsServiceEnabled:serviceType];
 
   // Set the network to use a cellular network, which should disable uploading
   // when the wifi-only flag is set.
   chrome_test_util::SetWWANStateTo(YES);
-  [[GREYUIThreadExecutor sharedInstance] drainUntilIdle];
+  chrome_test_util::WaitForBreakpadQueue();
   [self assertMetricsServiceEnabledButNotUploading:serviceType];
 
   // Turn off cellular network usage, which should enable uploading.
   chrome_test_util::SetWWANStateTo(NO);
-  [[GREYUIThreadExecutor sharedInstance] drainUntilIdle];
+  chrome_test_util::WaitForBreakpadQueue();
   [self assertMetricsServiceEnabled:serviceType];
 
   // kMetricsReportingEnabled ON and kMetricsReportingWifiOnly OFF
   [self setMetricsReportingEnabled:YES wifiOnly:NO];
   [self assertMetricsServiceEnabled:serviceType];
 #else
   // Development build.  Do not allow any recording or uploading of data.
   // Specifically, the kMetricsReportingEnabled preference is completely
   // disregarded for non-official builds, and checking its value always returns
   // false (NO).
@@ skipping 417 matching lines @@
       performAction:grey_tap()];
   [[EarlGrey selectElementWithMatcher:PrivacyButton()]
       performAction:grey_tap()];
   [[EarlGrey selectElementWithMatcher:SendUsageDataButton()]
       performAction:grey_tap()];
   chrome_test_util::VerifyAccessibilityForCurrentScreen();
   [self closeSubSettingsMenu];
 }
 
 @end