[google_maps] fix markersToChange to actually change modified markers

packages/google_maps_flutter/lib/src/marker.dart

@@ -274,15 +274,40 @@ class Marker {
   }
 
   @override
-  bool operator ==(Object other) {
-    if (identical(this, other)) return true;
-    if (other.runtimeType != runtimeType) return false;
-    final Marker typedOther = other;
-    return markerId == typedOther.markerId;
-  }
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      other is Marker &&
+          runtimeType == other.runtimeType &&
+          markerId == other.markerId &&
+          alpha == other.alpha &&
+          anchor == other.anchor &&
+          consumeTapEvents == other.consumeTapEvents &&
+          draggable == other.draggable &&
+          flat == other.flat &&
+          icon == other.icon &&
+          infoWindow == other.infoWindow &&
+          position == other.position &&
+          rotation == other.rotation &&
+          visible == other.visible &&
+          zIndex == other.zIndex &&
+          onTap == other.onTap;
 
   @override
-  int get hashCode => markerId.hashCode;
+  int get hashCode => hashValues(
+      markerId,
+      alpha,
+      anchor,
+      anchor,
+      consumeTapEvents,
+      draggable,
+      flat,
+      icon,
+      infoWindow,
+      position,
+      rotation,
+      visible,
+      zIndex,
+      onTap);
 
   @override
   String toString() {

packages/google_maps_flutter/lib/src/marker_updates.dart

@@ -24,6 +24,10 @@ class _MarkerUpdates {
     final Set<MarkerId> prevMarkerIds = previousMarkers.keys.toSet();
     final Set<MarkerId> currentMarkerIds = currentMarkers.keys.toSet();
 
+    final Set<Marker> previousMarkersSet =
+        Set<Marker>.of(previousMarkers.values);
+    final Set<Marker> currentMarkersSet = Set<Marker>.of(currentMarkers.values);
+
     Marker idToCurrentMarker(MarkerId id) {
       return currentMarkers[id];
     }
@@ -36,10 +40,9 @@ class _MarkerUpdates {
         .map(idToCurrentMarker)
         .toSet();
 
-    final Set<Marker> _markersToChange = currentMarkerIds
-        .intersection(prevMarkerIds)
-        .map(idToCurrentMarker)
-        .toSet();
+    final Set<Marker> _markersToChange = currentMarkersSet
+        .difference(previousMarkersSet)
+          ..removeAll(_markersToAdd);
 
     markersToAdd = _markersToAdd;
     markerIdsToRemove = _markerIdsToRemove;