【fix】修复不同图层设置掩膜，掩膜有相交时错乱的问题 review by xiongjj

Author: songyumeng

src/openlayers/core/Util.js

@@ -515,7 +515,7 @@ export class Util {
         Util.unsetMask(todoLayers);
         todoLayers.forEach((layer) => {
             layer.classNameBak_ = layer.className_;
-            layer.className_ = 'ol_mask_layer';
+            layer.className_ = `ol_mask_layer_${layer.ol_uid}`;
             layer.clipRender = clipRender;
             layer.extentBak_ = layer.getExtent();
             layer.setExtent(clipLayer.getSource().getExtent());

test/openlayers/core/UtilSpec.js

@@ -252,7 +252,7 @@ describe('openlayers_Util', () => {
         ]);
         Util.setMask(layer, polygon);
         expect(layer.classNameBak_).toBe('ol-layer');
-        expect(layer.className_).toBe('ol_mask_layer');
+        expect(layer.className_).toContain('ol_mask_layer_');
         expect(layer.clipRender).not.toBeNull;
         expect(layer.setExtent).toHaveBeenCalled;
         expect(layer.changed).toHaveBeenCalled;