Implement basic accessibility for IME candidate window.

Before this fix, assistive technologies (I tested with ChromeVox) were
unable to navigate into the IME candidates. For ChromeVox in particular,
using the arrow keys to navigate the candidates produced no speech
output.

With this fix, ChromeVox can navigate into the IME candidates and
speaks each candidate to the user.

Bug: 1034146
Change-Id: I77b584fc2a2648bc5f9fca479b2363d476628ac4
Relnotes: Make Chrome IME accessible to assistive technology.
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2151672Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Akihiro Ota <akihiroota@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760099}

ui/chromeos/BUILD.gn

@@ -42,6 +42,7 @@ component("chromeos") {
     "//services/device/public/mojom",
     "//services/service_manager/public/cpp",
     "//skia",
+    "//ui/accessibility:ax_base",
     "//ui/aura",
     "//ui/base",
     "//ui/base/ime",

ui/chromeos/ime/candidate_view.cc

@@ -2,10 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "ui/chromeos/ime/candidate_view.h"
+
 #include "base/macros.h"
 #include "base/strings/utf_string_conversions.h"
+#include "ui/accessibility/ax_enums.mojom.h"
+#include "ui/accessibility/ax_node_data.h"
 #include "ui/base/ime/candidate_window.h"
-#include "ui/chromeos/ime/candidate_view.h"
 #include "ui/chromeos/ime/candidate_window_constants.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/native_theme/native_theme.h"
@@ -177,6 +180,7 @@ void CandidateView::SetHighlighted(bool highlighted) {
 
   highlighted_ = highlighted;
   if (highlighted) {
+    NotifyAccessibilityEvent(ax::mojom::Event::kSelection, false);
     ui::NativeTheme* theme = GetNativeTheme();
     SetBackground(views::CreateSolidBackground(theme->GetSystemColor(
         ui::NativeTheme::kColorId_TextfieldSelectionBackgroundFocused)));
@@ -280,5 +284,10 @@ gfx::Size CandidateView::CalculatePreferredSize() const {
   return size;
 }
 
+void CandidateView::GetAccessibleNodeData(ui::AXNodeData* node_data) {
+  node_data->SetName(candidate_label_->GetText());
+  node_data->role = ax::mojom::Role::kMenuItem;
+}
+
 }  // namespace ime
 }  // namespace ui

ui/chromeos/ime/candidate_view.h

@@ -48,6 +48,7 @@ class UI_CHROMEOS_EXPORT CandidateView : public views::Button {
   bool OnMouseDragged(const ui::MouseEvent& event) override;
   void Layout() override;
   gfx::Size CalculatePreferredSize() const override;
+  void GetAccessibleNodeData(ui::AXNodeData* node_data) override;
 
   // The orientation of the candidate view.
   ui::CandidateWindow::Orientation orientation_;

ui/chromeos/ime/candidate_window_view.cc

@@ -10,6 +10,8 @@
 
 #include "base/macros.h"
 #include "base/strings/utf_string_conversions.h"
+#include "ui/accessibility/ax_enums.mojom.h"
+#include "ui/accessibility/ax_node_data.h"
 #include "ui/chromeos/ime/candidate_view.h"
 #include "ui/chromeos/ime/candidate_window_constants.h"
 #include "ui/display/display.h"
@@ -411,5 +413,9 @@ void CandidateWindowView::ButtonPressed(views::Button* sender,
   }
 }
 
+void CandidateWindowView::GetAccessibleNodeData(ui::AXNodeData* node_data) {
+  node_data->role = ax::mojom::Role::kMenu;
+}
+
 }  // namespace ime
 }  // namespace ui

ui/chromeos/ime/candidate_window_view.h

@@ -83,6 +83,9 @@ class UI_CHROMEOS_EXPORT CandidateWindowView
   // Overridden from views::ButtonListener:
   void ButtonPressed(views::Button* sender, const ui::Event& event) override;
 
+  // Overridden from View:
+  void GetAccessibleNodeData(ui::AXNodeData* node_data) override;
+
   void SelectCandidateAt(int index_in_page);
   void UpdateVisibility();