Only trigger attributeChangedCallback on toggleAttribute if the value changed

Author: jessevanassen

packages/scoped-custom-element-registry/src/scoped-custom-element-registry.js

@@ -354,7 +354,10 @@ if (!ShadowRoot.prototype.createElement) {
           const old = this.getAttribute(name);
           toggleAttribute.call(this, name, force);
           const newValue = this.getAttribute(name);
-          attributeChangedCallback.call(this, name, old, newValue);
+
+          if (old !== newValue) {
+            attributeChangedCallback.call(this, name, old, newValue);
+          }
         } else {
           toggleAttribute.call(this, name, force);
         }