Make customizable select <button> display:contents

This patch makes the <select> element itself handle focus, interaction,
and box decorations instead of the child <button> element. This removes
a lot of complexity, including delegatesFocus, divergent event handling
and button testing, and :-internal-select-has-child-button.

This was discussed here:
w3c/csswg-drafts#10857

Change-Id: Ia036c6dc08be1b86a50bd96239d08ad19c9a7a6b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6001193
Reviewed-by: David Baron <[email protected]>
Commit-Queue: Joey Arhar <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1383048}

html/semantics/forms/the-select-element/customizable-select/button-in-popover.tentative.html

@@ -22,10 +22,9 @@
 <script>
 promise_test(async () => {
   const select = document.querySelector('select');
-  const invokerButton = document.getElementById('invoker');
   const popoverButton = document.getElementById('popover');
 
-  await test_driver.click(invokerButton);
+  await test_driver.click(select);
   assert_true(select.matches(':open'),
     'Select should open after clicking the invoker button.');
 

html/semantics/forms/the-select-element/customizable-select/select-anchor-regression.html

@@ -39,7 +39,7 @@
 
 <script>
 promise_test(async () => {
-  await test_driver.click(document.querySelector('button'));
+  await test_driver.click(document.querySelector('select'));
   await new Promise(requestAnimationFrame);
 }, 'This test passes if it does not crash.');
 </script>

html/semantics/forms/the-select-element/customizable-select/select-disabled.tentative.html

@@ -34,10 +34,6 @@
       button.focus();
       assert_not_equals(document.activeElement, button,
         'select button should not be focusable when select is disabled.');
-
-      await test_driver.click(button);
-      assert_false(select.matches(':open'),
-        'select should not be open after clicking button when disabled.');
     }
   }, `${id}: <select disabled> should prevent focus and activation with appearance:base-select.`);
 });

html/semantics/forms/the-select-element/customizable-select/select-keyboard-behavior.tentative.html

@@ -68,15 +68,7 @@
 
   promise_test(async t => {
     addCloseCleanup(t);
-    // TODO(http://crbug.com/1350299): When focus for custom buttons is fixed,
-    // then we shouldn't need to explicitly focus the custom button like this
-    // anymore.
-    const customButton = select.querySelector('button');
-    if (customButton) {
-      customButton.focus();
-    } else {
-      select.focus();
-    }
+    select.focus();
     assert_false(select.matches(':open'),
       'The select should initially be closed.');
     await test_driver.send_keys(document.activeElement, Space);
@@ -85,7 +77,7 @@
       'The select should be open after pressing space.');
 
     await test_driver.send_keys(document.activeElement, Escape);
-    assert_equals(document.activeElement, customButton ? customButton : select,
+    assert_equals(document.activeElement, select,
       'After dismissing the popover, the invoker button should be focused again.');
   }, `${id}: When the listbox is closed, spacebar should open the listbox.`);
 
@@ -131,15 +123,7 @@
   promise_test(async t => {
     addCloseCleanup(t);
 
-    // TODO(http://crbug.com/1350299): When focus for custom buttons is fixed,
-    // then we shouldn't need to explicitly use the custom button like this
-    // anymore.
-    const customButton = select.querySelector('button');
-    if (customButton) {
-      await test_driver.send_keys(customButton, Enter);
-    } else {
-      await test_driver.send_keys(select, Enter);
-    }
+    await test_driver.send_keys(select, Enter);
     await new Promise(requestAnimationFrame);
     assert_false(select.matches(':open'),
       'Enter should not open the listbox when outside a form.');
@@ -150,11 +134,7 @@
       event.preventDefault();
       formWasSubmitted = true;
     }, {once: true});
-    if (customButton) {
-      await test_driver.send_keys(customButton, Enter);
-    } else {
-      await test_driver.send_keys(select, Enter);
-    }
+    await test_driver.send_keys(select, Enter);
     await new Promise(requestAnimationFrame);
     assert_true(formWasSubmitted,
       'Enter should submit the form when the listbox is closed.');
@@ -214,14 +194,8 @@
   promise_test(async t => {
     addCloseCleanup(t);
 
-    const customButton = select.querySelector('button');
-    if (customButton) {
-      customButton.focus();
-      await test_driver.send_keys(customButton, Space);
-    } else {
-      select.focus();
-      await test_driver.send_keys(select, Space);
-    }
+    select.focus();
+    await test_driver.send_keys(select, Space);
     assert_true(select.matches(':open'),
       'Space should open the listbox.');
     assert_equals(document.activeElement, select.querySelector('.one'),
@@ -234,12 +208,7 @@
     // TODO(crbug.com/40263709): Remove this blur when focus on close is improved.
     document.activeElement.blur();
 
-    if (customButton) {
-      customButton.focus();
-      await test_driver.send_keys(customButton, Space);
-    } else {
-      await test_driver.send_keys(select, Space);
-    }
+    await test_driver.send_keys(select, Space);
     assert_true(select.matches(':open'),
       'Second space should open the listbox.');
     assert_equals(document.activeElement, select.querySelector('.one'),

html/semantics/forms/the-select-element/customizable-select/select-mouse-behavior.tentative.html

@@ -74,13 +74,8 @@
 
   promise_test(async () => {
     await test_driver.click(label);
-    if (button) {
-      assert_equals(document.activeElement, button,
-        'select child button should be the active element after clicking the label.');
-    } else {
-      assert_equals(document.activeElement, select,
-        'select should be the active element after clicking the label.');
-    }
+    assert_equals(document.activeElement, select,
+      'select should be the active element after clicking the label.');
     assert_false(select.matches(':open'),
       'select picker should be closed after clicking the label.');
   }, `${id}: Clicking the label should focus the select button without opening the picker.`);