[google_maps_flutter] Fix integration tests (flutter#6350)

Some integration tests behave slightly differently on Android when using
Hybrid Composition, and need to wait for a change to become true rather
than it being immediately true.

This replicates the changes from `google_maps_flutter_android` to the
app-facing copy of those integration tests.

Fixes tree breakage from publishing
flutter#6334

packages/google_maps_flutter/google_maps_flutter/example/integration_test/google_maps_test.dart

@@ -22,6 +22,28 @@ void main() {
   IntegrationTestWidgetsFlutterBinding.ensureInitialized();
   GoogleMapsFlutterPlatform.instance.enableDebugInspection();
 
+  // Repeatedly checks an asynchronous value against a test condition, waiting
+  // one frame between each check, returing the value if it passes the predicate
+  // before [maxTries] is reached.
+  //
+  // Returns null if the predicate is never satisfied.
+  //
+  // This is useful for cases where the Maps SDK has some internally
+  // asynchronous operation that we don't have visibility into (e.g., native UI
+  // animations).
+  Future<T?> waitForValueMatchingPredicate<T>(WidgetTester tester,
+      Future<T> Function() getValue, bool Function(T) predicate,
+      {int maxTries = 100}) async {
+    for (int i = 0; i < maxTries; i++) {
+      final T value = await getValue();
+      if (predicate(value)) {
+        return value;
+      }
+      await tester.pump();
+    }
+    return null;
+  }
+
   testWidgets('testCompassToggle', (WidgetTester tester) async {
     final Key key = GlobalKey();
     final Completer<int> mapIdCompleter = Completer<int>();
@@ -481,12 +503,13 @@ void main() {
     final GoogleMapController mapController =
         await mapControllerCompleter.future;
 
+    // Wait for the visible region to be non-zero.
     final LatLngBounds firstVisibleRegion =
-        await mapController.getVisibleRegion();
-
-    expect(firstVisibleRegion, isNotNull);
-    expect(firstVisibleRegion.southwest, isNotNull);
-    expect(firstVisibleRegion.northeast, isNotNull);
+        await waitForValueMatchingPredicate<LatLngBounds>(
+                tester,
+                () => mapController.getVisibleRegion(),
+                (LatLngBounds bounds) => bounds != zeroLatLngBounds) ??
+            zeroLatLngBounds;
     expect(firstVisibleRegion, isNot(zeroLatLngBounds));
     expect(firstVisibleRegion.contains(_kInitialMapCenter), isTrue);
 
@@ -517,9 +540,6 @@ void main() {
     final LatLngBounds secondVisibleRegion =
         await mapController.getVisibleRegion();
 
-    expect(secondVisibleRegion, isNotNull);
-    expect(secondVisibleRegion.southwest, isNotNull);
-    expect(secondVisibleRegion.northeast, isNotNull);
     expect(secondVisibleRegion, isNot(zeroLatLngBounds));
 
     expect(firstVisibleRegion, isNot(secondVisibleRegion));
@@ -906,7 +926,13 @@ void main() {
     expect(iwVisibleStatus, false);
 
     await controller.showMarkerInfoWindow(marker.markerId);
-    iwVisibleStatus = await controller.isMarkerInfoWindowShown(marker.markerId);
+    // The Maps SDK doesn't always return true for whether it is shown
+    // immediately after showing it, so wait for it to report as shown.
+    iwVisibleStatus = await waitForValueMatchingPredicate<bool>(
+            tester,
+            () => controller.isMarkerInfoWindowShown(marker.markerId),
+            (bool visible) => visible) ??
+        false;
     expect(iwVisibleStatus, true);
 
     await controller.hideMarkerInfoWindow(marker.markerId);