Ash Tray: Fix Search+Space not toggling notification enabled setting.

When ChromeVox is enabled, Search+Space simulates a mouse press, which was not
being forwarded properly to the child contents in NotifierSettingsView.

TEST=manually verified
BUG=897974

Change-Id: I13a738034891ac7d073c30d86daa3a3e98e321ea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1666309Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Tim Song <tengs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#670331}

ash/system/message_center/notifier_settings_view.cc

@@ -116,6 +116,8 @@ class NotifierButtonWrapperView : public views::View {
   void OnFocus() override;
   bool OnKeyPressed(const ui::KeyEvent& event) override;
   bool OnKeyReleased(const ui::KeyEvent& event) override;
+  bool OnMousePressed(const ui::MouseEvent& event) override;
+  void OnMouseReleased(const ui::MouseEvent& event) override;
   void OnPaint(gfx::Canvas* canvas) override;
   void OnBlur() override;
   const char* GetClassName() const override;
@@ -192,6 +194,14 @@ bool NotifierButtonWrapperView::OnKeyReleased(const ui::KeyEvent& event) {
   return contents_->OnKeyReleased(event);
 }
 
+bool NotifierButtonWrapperView::OnMousePressed(const ui::MouseEvent& event) {
+  return contents_->OnMousePressed(event);
+}
+
+void NotifierButtonWrapperView::OnMouseReleased(const ui::MouseEvent& event) {
+  contents_->OnMouseReleased(event);
+}
+
 void NotifierButtonWrapperView::OnPaint(gfx::Canvas* canvas) {
   View::OnPaint(canvas);
   views::Painter::PaintFocusPainter(this, canvas, focus_painter_.get());