[ios] Fix testRepostForm egtests on SlimNav iOS13.

Because synchronization has to be disabled for this portion of the test, add a
half second delay to allow the new iOS13 confirmation dialog to be fully
visible.

Bug: 989615
Change-Id: Ia5322dfc5c67ae4609922b6d883434fc2843a27f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1727652Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Justin Cohen <justincohen@chromium.org>
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#682814}

ios/chrome/browser/web/forms_egtest.mm

@@ -238,6 +238,11 @@ id<GREYMatcher> ResendPostButtonMatcher() {
         std::make_unique<ScopedSynchronizationDisabler>();
     if (![ChromeEarlGrey isSlimNavigationManagerEnabled]) {
       disabler.reset();
+    } else {
+      // TODO(crbug.com/989615): Investigate why this is necessary even with a
+      // visible check below.
+      base::test::ios::SpinRunLoopWithMinDelay(
+          base::TimeDelta::FromSecondsD(0.5));
     }
 
     [ChromeEarlGrey
@@ -285,6 +290,11 @@ id<GREYMatcher> ResendPostButtonMatcher() {
         std::make_unique<ScopedSynchronizationDisabler>();
     if (![ChromeEarlGrey isSlimNavigationManagerEnabled]) {
       disabler.reset();
+    } else {
+      // TODO(crbug.com/989615): Investigate why this is necessary even with a
+      // visible check below.
+      base::test::ios::SpinRunLoopWithMinDelay(
+          base::TimeDelta::FromSecondsD(0.5));
     }
 
     [ChromeEarlGrey
@@ -331,6 +341,11 @@ id<GREYMatcher> ResendPostButtonMatcher() {
         std::make_unique<ScopedSynchronizationDisabler>();
     if (![ChromeEarlGrey isSlimNavigationManagerEnabled]) {
       disabler.reset();
+    } else {
+      // TODO(crbug.com/989615): Investigate why this is necessary even with a
+      // visible check below.
+      base::test::ios::SpinRunLoopWithMinDelay(
+          base::TimeDelta::FromSecondsD(0.5));
     }
 
     [ChromeEarlGrey