add customelements getName

Bug: 1435389
Change-Id: Iae61c730737d0f2f0e42cbe7d3e000eb38365b65
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4466232
Reviewed-by: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1155095}

custom-elements/CustomElementRegistry.html

@@ -623,6 +623,45 @@
     assert_equals(customElements.get('existing-custom-element'), ExistingCustomElement);
 }, 'customElements.get return the constructor of the entry with the given name when there is a matching entry.');
 
+test(function () {
+  assert_equals(customElements.getName(class extends HTMLElement {}), null);
+}, 'customElements.getName must return null when the registry does not contain an entry with the given constructor');
+
+test(function () {
+  assert_throws_js(TypeError, function () { customElements.getName(undefined); },
+        'customElements.getName must throw a TypeError when the element interface is undefined');
+  assert_throws_js(TypeError, function () { customElements.getName(null); },
+        'customElements.getName must throw a TypeError when the element interface is null');
+  assert_throws_js(TypeError, function () { customElements.getName('foo-bar'); },
+        'customElements.getName must throw a TypeError when the element interface is a string');
+  assert_throws_js(TypeError, function () { customElements.getName(1); },
+        'customElements.getName must throw a TypeError when the element interface is a number');
+  assert_throws_js(TypeError, function () { customElements.getName({}); },
+        'customElements.getName must throw a TypeError when the element interface is an object');
+  assert_throws_js(TypeError, function () { customElements.getName([]) },
+        'customElements.getName must throw a TypeError when the element interface is an array');
+}, 'customElements.getName must throw when the element interface is not a constructor');
+
+test(function () {
+    class OtherExistingCustomElement extends HTMLElement {};
+    class SecondExistingCustomElement extends HTMLElement {};
+    assert_throws_js(TypeError, function () { customElements.getName(customElements.getName(OtherExistingCustomElement)); },
+        'customElements.getName must throw a TypeError when the element interface is undefined');
+    customElements.define('other-existing-custom-element', OtherExistingCustomElement);
+    customElements.define('second-existing-custom-element', SecondExistingCustomElement);
+    assert_equals(customElements.getName(OtherExistingCustomElement), 'other-existing-custom-element');
+    assert_equals(customElements.getName(SecondExistingCustomElement), 'second-existing-custom-element');
+}, 'customElements.getName returns the name of the entry with the given constructor when there is a matching entry.');
+
+test(function () {
+    class ButtonCustomBuiltInElement extends HTMLButtonElement {};
+    class InputCustomBuiltInElement extends HTMLInputElement {};
+    customElements.define('button-custom-built-in-element', ButtonCustomBuiltInElement, { extends: 'button' });
+    customElements.define('input-custom-built-in-element', InputCustomBuiltInElement, { extends: 'input' });
+    assert_equals(customElements.getName(ButtonCustomBuiltInElement), 'button-custom-built-in-element');
+    assert_equals(customElements.getName(InputCustomBuiltInElement), 'input-custom-built-in-element');
+}, 'customElements.getName returns the name of the entry with the given customized built in constructor when there is a matching entry.');
+
 test(function () {
     assert_true(customElements.whenDefined('some-name') instanceof Promise);
 }, 'customElements.whenDefined must return a promise for a valid custom element name');