[md] Fixes tooltips on Linux that should not have changed

ui/views/corewm/tooltip_aura.cc

Index: ui/views/corewm/tooltip_aura.cc
diff --git a/ui/views/corewm/tooltip_aura.cc b/ui/views/corewm/tooltip_aura.cc
index f33eaca7d4084325afd9d1a70ebb42f21d475687..7bf43adec87109e1ff051f64450d065e5b2e6c81 100644
--- a/ui/views/corewm/tooltip_aura.cc
+++ b/ui/views/corewm/tooltip_aura.cc
@@ -29,13 +29,19 @@ namespace {
 // be wrapped.
 const int kTooltipMaxWidthPixels = 400;
 
-// Corner radius of tooltip background used with Material Design.
-const float kTooltipCornerRadius = 2.f;
-
 // FIXME: get cursor offset from actual cursor size.
 const int kCursorOffsetX = 10;
 const int kCursorOffsetY = 15;
 
+// TODO(varkha): Update if native widget can be transparent on Linux.
+bool CanUseTranslucentTooltipWidget() {
+#if defined(OS_LINUX) && !defined(OS_CHROMEOS)
+  return false;
+#else
+  return ui::MaterialDesignController::IsModeMaterial();
+#endif
+}
+
 // Creates a widget of type TYPE_TOOLTIP
 views::Widget* CreateTooltipWidget(aura::Window* tooltip_window) {
   views::Widget* widget = new views::Widget;
@@ -47,10 +53,10 @@ views::Widget* CreateTooltipWidget(aura::Window* tooltip_window) {
   DCHECK(params.context);
   params.keep_on_top = true;
   params.accept_events = false;
-  if (ui::MaterialDesignController::IsModeMaterial()) {
+  if (CanUseTranslucentTooltipWidget())
     params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
+  if (ui::MaterialDesignController::IsModeMaterial())
     params.shadow_type = views::Widget::InitParams::SHADOW_TYPE_NONE;
-  }
   widget->Init(params);
   return widget;
 }
@@ -119,8 +125,10 @@ class TooltipAura::TooltipView : public views::View {
   }
 
   void SetBackgroundColor(SkColor background_color) {
+    // Corner radius of tooltip background used with Material Design.
+    const float kTooltipCornerRadius = 2.f;
     views::Background* background =
-        ui::MaterialDesignController::IsModeMaterial()
+        CanUseTranslucentTooltipWidget()
             ? views::Background::CreateBackgroundPainter(
                   true, views::Painter::CreateSolidRoundRectPainter(
                             background_color, kTooltipCornerRadius))