feat: improve TouchBarButton accessibility

docs/api/touch-bar-button.md

@@ -8,16 +8,23 @@ Process: [Main](../tutorial/application-architecture.md#main-and-renderer-proces
 
 * `options` Object
   * `label` String (optional) - Button text.
+  * `accessibilityLabel` String (optional) - A short description of the button for use by screenreaders like VoiceOver.
   * `backgroundColor` String (optional) - Button background color in hex format,
     i.e `#ABCDEF`.
   * `icon` [NativeImage](native-image.md) | String (optional) - Button icon.
   * `iconPosition` String (optional) - Can be `left`, `right` or `overlay`. Defaults to `overlay`.
   * `click` Function (optional) - Function to call when the button is clicked.
 
+If you choose to define the `accessibilityLabel`, ensure you have considered macOS [best practices](https://developer.apple.com/documentation/appkit/nsaccessibilitybutton/1524910-accessibilitylabel?language=objc).
+
 ### Instance Properties
 
 The following properties are available on instances of `TouchBarButton`:
 
+#### `touchBarButton.accessibilityLabel`
+
+A `String` representing the description of the button to be read by a screen reader. Will only be read by screen readers if no label is set.
+
 #### `touchBarButton.label`
 
 A `String` representing the button's current text. Changing this value immediately updates the button

lib/browser/api/touch-bar.js

@@ -191,8 +191,9 @@ TouchBar.TouchBarButton = class TouchBarButton extends TouchBarItem {
     super()
     if (config == null) config = {}
     this._addImmutableProperty('type', 'button')
-    const { click, icon, iconPosition, label, backgroundColor } = config
+    const { click, icon, iconPosition, label, backgroundColor, accessibilityLabel } = config
     this._addLiveProperty('label', label)
+    this._addLiveProperty('accessibilityLabel', accessibilityLabel)
     this._addLiveProperty('backgroundColor', backgroundColor)
     this._addLiveProperty('icon', icon)
     this._addLiveProperty('iconPosition', iconPosition)

shell/browser/ui/cocoa/atom_touch_bar.mm

@@ -363,6 +363,10 @@ - (void)updateButton:(NSCustomTouchBarItem*)item
     button.bezelColor = nil;
   }
 
+  std::string accessibilityLabel;
+  settings.Get("accessibilityLabel", &accessibilityLabel);
+  button.accessibilityLabel = base::SysUTF8ToNSString(accessibilityLabel);
+
   std::string label;
   settings.Get("label", &label);
   button.title = base::SysUTF8ToNSString(label);