Remove circle background from close button in Select-to-speak panel.

For consistency with autoclick panel, feedback from UX review.

Bug: 1140216
Change-Id: I324ce723bc9e5c69be8f3fe39a7aba4ce2ed27db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626924Reviewed-by: Katie Dektar <katie@chromium.org>
Commit-Queue: Joel Riley <joelriley@google.com>
Cr-Commit-Position: refs/heads/master@{#843209}

ash/system/accessibility/select_to_speak_menu_view.cc

@@ -148,6 +148,7 @@ SelectToSpeakMenuView::SelectToSpeakMenuView(Delegate* delegate)
                         .CopyAddressTo(&stop_button_)
                         .SetID(static_cast<int>(ButtonId::kStop))
                         .SetVectorIcon(kSelectToSpeakStopIcon)
+                        .SetDrawHighlight(false)
                         .SetPreferredSize(gfx::Size(kButtonSize, kButtonSize))
                         .SetTooltipText(l10n_util::GetStringUTF16(
                             IDS_ASH_SELECT_TO_SPEAK_EXIT))