Improve a11y state for ToggleButton.

ui/views/controls/button/toggle_button.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/button/toggle_button.h"
 
 #include "third_party/skia/include/core/SkDrawLooper.h"
 #include "third_party/skia/include/core/SkPaint.h"
+#include "ui/accessibility/ax_node_data.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/color_palette.h"
 #include "ui/gfx/color_utils.h"
 #include "ui/views/animation/ink_drop_ripple.h"
 #include "ui/views/border.h"
 
 namespace views {
 
 namespace {
 
@@ skipping 175 matching lines @@
 }
 
 void ToggleButton::OnBoundsChanged(const gfx::Rect& previous_bounds) {
   UpdateThumb();
 }
 
 void ToggleButton::OnNativeThemeChanged(const ui::NativeTheme* theme) {
   SchedulePaint();
 }
 
+void ToggleButton::GetAccessibleNodeData(ui::AXNodeData* node_data) {
+  CustomButton::GetAccessibleNodeData(node_data);
+
+  node_data->role = ui::AX_ROLE_SWITCH;
+  if (is_on_)
+    node_data->AddStateFlag(ui::AX_STATE_CHECKED);
+}
+
 void ToggleButton::AddInkDropLayer(ui::Layer* ink_drop_layer) {
   thumb_view_->AddInkDropLayer(ink_drop_layer);
 }
 
 void ToggleButton::RemoveInkDropLayer(ui::Layer* ink_drop_layer) {
   thumb_view_->RemoveInkDropLayer(ink_drop_layer);
 }
 
 std::unique_ptr<InkDropRipple> ToggleButton::CreateInkDropRipple() const {
   gfx::Rect rect = thumb_view_->GetLocalBounds();
@@ skipping 14 matching lines @@
     // TODO(varkha, estade): The thumb is using its own view. Investigate if
     // repainting in every animation step to update colors could be avoided.
     UpdateThumb();
     SchedulePaint();
     return;
   }
   CustomButton::AnimationProgressed(animation);
 }
 
 }  // namespace views