[iOS] Tell voiceover that two buttons in sync settings are buttons

These two items didn't have button set on their accessibility traits.

Bug: 979696
Change-Id: I117a10155ca13a23145320f6296640fd7154d454
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1815122Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: Robbie Gibson <rkgibson@google.com>
Cr-Commit-Position: refs/heads/master@{#698517}

ios/chrome/browser/ui/settings/google_services/manage_sync_settings_mediator.mm

@@ -252,6 +252,7 @@ NSString* kGoogleServicesSyncErrorImage = @"google_services_sync_error";
       GetNSString(IDS_IOS_MANAGE_SYNC_GOOGLE_ACTIVITY_CONTROLS_TITLE);
   googleActivityControlsItem.detailText =
       GetNSString(IDS_IOS_MANAGE_SYNC_GOOGLE_ACTIVITY_CONTROLS_DESCRIPTION);
+  googleActivityControlsItem.accessibilityTraits |= UIAccessibilityTraitButton;
   [model addItem:googleActivityControlsItem
       toSectionWithIdentifier:AdvancedSettingsSectionIdentifier];
 
@@ -264,6 +265,7 @@ NSString* kGoogleServicesSyncErrorImage = @"google_services_sync_error";
       GetNSString(IDS_IOS_MANAGE_SYNC_DATA_FROM_CHROME_SYNC_DESCRIPTION);
   dataFromChromeSyncItem.accessibilityIdentifier =
       kDataFromChromeSyncAccessibilityIdentifier;
+  dataFromChromeSyncItem.accessibilityTraits |= UIAccessibilityTraitButton;
   [model addItem:dataFromChromeSyncItem
       toSectionWithIdentifier:AdvancedSettingsSectionIdentifier];
 }