Remove button_drop_down accessibility role

It's not necessary, as a role of "button" with the
"has pop up" state is fully supported and sufficient.
The button_drop_down role wasn't even being mapped
correctly on Windows, leading to inconsistent feedback
with some screen readers.

Bug: 766856

Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ib7f631a759ab44ffc3307204bcc74a9471afc22a
Reviewed-on: https://chromium-review.googlesource.com/842475Reviewed-by: David Tseng <dtseng@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#531363}

chrome/browser/resources/chromeos/chromevox/cvox2/background/automation_predicate.js

@@ -162,7 +162,7 @@ AutomationPredicate.focused = function(node) {
  */
 AutomationPredicate.leaf = function(node) {
   return !node.firstChild || node.role == Role.BUTTON ||
-      node.role == Role.BUTTON_DROP_DOWN || node.role == Role.POP_UP_BUTTON ||
+      node.role == Role.POP_UP_BUTTON ||
       node.role == Role.SLIDER || node.role == Role.TEXT_FIELD ||
       node.state[State.INVISIBLE] || node.children.every(function(n) {
         return n.state[State.INVISIBLE];

chrome/browser/ui/views/toolbar/toolbar_button.cc

@@ -127,7 +127,7 @@ void ToolbarButton::OnGestureEvent(ui::GestureEvent* event) {
 
 void ToolbarButton::GetAccessibleNodeData(ui::AXNodeData* node_data) {
   Button::GetAccessibleNodeData(node_data);
-  node_data->role = ui::AX_ROLE_BUTTON_DROP_DOWN;
+  node_data->role = ui::AX_ROLE_BUTTON;
   node_data->AddState(ui::AX_STATE_HASPOPUP);
   if (enabled()) {
     node_data->AddIntAttribute(ui::AX_ATTR_DEFAULT_ACTION_VERB,

chrome/common/extensions/api/automation.idl

@@ -76,7 +76,6 @@
     banner,
     blockquote,
     button,
-    buttonDropDown,
     canvas,
     caption,
     caret,

content/app/strings/content_strings.grd

@@ -341,9 +341,6 @@ below:
         <message name="IDS_AX_ROLE_BUTTON" desc="Accessibility role description for a button">
           button
         </message>
-        <message name="IDS_AX_ROLE_BUTTON_DROP_DOWN" desc="Accessibility role description for a button that drops down">
-          drop down button
-        </message>
         <message name="IDS_AX_ROLE_CELL" desc="Accessibility role description for a cell, like in a table or grid">
           cell
         </message>

content/browser/accessibility/browser_accessibility_android.cc

@@ -502,9 +502,6 @@ base::string16 BrowserAccessibilityAndroid::GetRoleDescription() const {
     case ui::AX_ROLE_BUTTON:
       message_id = IDS_AX_ROLE_BUTTON;
       break;
-    case ui::AX_ROLE_BUTTON_DROP_DOWN:
-      message_id = IDS_AX_ROLE_BUTTON_DROP_DOWN;
-      break;
     case ui::AX_ROLE_CANVAS:
       // No role description.
       break;

third_party/closure_compiler/externs/automation.js

@@ -87,7 +87,6 @@ chrome.automation.RoleType = {
   BANNER: 'banner',
   BLOCKQUOTE: 'blockquote',
   BUTTON: 'button',
-  BUTTON_DROP_DOWN: 'buttonDropDown',
   CANVAS: 'canvas',
   CAPTION: 'caption',
   CARET: 'caret',

ui/accessibility/ax_enums.idl

@@ -88,7 +88,6 @@
     banner,
     blockquote,
     button,
-    button_drop_down,  // Not used on Web.
     canvas,
     caption,
     caret,

ui/accessibility/platform/ax_platform_node_win.cc

@@ -2710,7 +2710,6 @@ int AXPlatformNodeWin::MSAARole() {
 
     // TODO(dmazzoni): figure out the proper MSAA role for roles listed below.
     case AX_ROLE_BLOCKQUOTE:
-    case AX_ROLE_BUTTON_DROP_DOWN:
     case AX_ROLE_CARET:
     case AX_ROLE_CLIENT:
     case AX_ROLE_DEFINITION: