WebUI[MD-refresh]: on init, cr-checkbox should not alter tabindex if not disabled.

When initializing, cr-checkbox unnecessarily set tabindex to 0 even if it
was set to something else. This CL fixes it

Bug: 839277
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I73d6e97ad7b6be8b7cd18759f1677f65acf96947
Reviewed-on: https://chromium-review.googlesource.com/1042864
Commit-Queue: Scott Chen <scottchen@chromium.org>
Reviewed-by: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556293}

chrome/test/data/webui/cr_elements/cr_checkbox_test.js

@@ -8,14 +8,14 @@ suite('cr-checkbox', function() {
   setup(function() {
     PolymerTest.clearBody();
     document.body.innerHTML = `
-      <cr-checkbox id="checkbox">
-        <div id="label">label
-          <a id="link">link</a>
+      <cr-checkbox>
+        <div>label
+          <a>link</a>
         </div>
       </cr-checkbox>
     `;
 
-    checkbox = document.getElementById('checkbox');
+    checkbox = document.querySelector('cr-checkbox');
     assertNotChecked();
   });
 
@@ -143,7 +143,7 @@ suite('cr-checkbox', function() {
     });
 
     assertNotChecked();
-    link = document.getElementById('link');
+    link = document.querySelector('a');
     link.click();
     assertNotChecked();
 
@@ -153,4 +153,29 @@ suite('cr-checkbox', function() {
     // Wait 1 cycle to make sure change-event was not fired.
     setTimeout(done);
   });
+
+  test('InitializingWithTabindex', function() {
+    PolymerTest.clearBody();
+    document.body.innerHTML = `
+      <cr-checkbox id="checkbox" tabindex="-1"></cr-checkbox>
+    `;
+
+    checkbox = document.querySelector('cr-checkbox');
+
+    // Should not override tabindex if it is initialized.
+    assertEquals(-1, checkbox.tabIndex);
+  });
+
+
+  test('InitializingWithDisabled', function() {
+    PolymerTest.clearBody();
+    document.body.innerHTML = `
+      <cr-checkbox id="checkbox" disabled></cr-checkbox>
+    `;
+
+    checkbox = document.querySelector('cr-checkbox');
+
+    // Initializing with disabled should make tabindex="-1".
+    assertEquals(-1, checkbox.tabIndex);
+  });
 });

ui/webui/resources/cr_elements/cr_checkbox/cr_checkbox.js

@@ -55,8 +55,15 @@ Polymer({
     this.setAttribute('aria-checked', this.checked ? 'true' : 'false');
   },
 
-  /** @private */
-  disabledChanged_: function() {
+  /**
+   * @param {boolean} current
+   * @param {boolean} previous
+   * @private
+   */
+  disabledChanged_: function(current, previous) {
+    if (previous === undefined && !this.disabled)
+      return;
+
     this.setAttribute('tabindex', this.disabled ? -1 : 0);
     this.setAttribute('aria-disabled', this.disabled ? 'true' : 'false');
   },