[Lacros] Enable overlay scrollbars

Bug: 1141261
Change-Id: I9f877ac89f9435193f04c87a6a3f3d51593f202d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2495516Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Darin Fisher <darin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820496}

ui/native_theme/BUILD.gn

@@ -59,6 +59,7 @@ component("native_theme") {
   deps = [
     "//base",
     "//base/third_party/dynamic_annotations",
+    "//build:chromeos_buildflags",
     "//cc/paint",
     "//ui/base",
     "//ui/color",

ui/native_theme/native_theme_aura.cc

@@ -11,6 +11,7 @@
 #include "base/notreached.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
+#include "build/chromeos_buildflags.h"
 #include "cc/paint/paint_canvas.h"
 #include "cc/paint/paint_flags.h"
 #include "third_party/skia/include/core/SkPath.h"
@@ -75,7 +76,7 @@ NativeThemeAura::NativeThemeAura(bool use_overlay_scrollbars,
     : NativeThemeBase(should_only_use_dark_colors),
       use_overlay_scrollbars_(use_overlay_scrollbars) {
 // We don't draw scrollbar buttons.
-#if defined(OS_CHROMEOS)
+#if defined(OS_CHROMEOS) || BUILDFLAG(IS_LACROS)
   set_scrollbar_button_length(0);
 #endif
 

ui/native_theme/native_theme_features.cc

@@ -5,10 +5,12 @@
 #include "ui/native_theme/native_theme_features.h"
 
 #include "build/build_config.h"
+#include "build/chromeos_buildflags.h"
 
 namespace features {
 
-#if defined(OS_ANDROID) || defined(OS_CHROMEOS) || defined(OS_FUCHSIA)
+#if defined(OS_ANDROID) || defined(OS_CHROMEOS) || defined(OS_FUCHSIA) || \
+    BUILDFLAG(IS_LACROS)
 constexpr base::FeatureState kOverlayScrollbarFeatureState =
     base::FEATURE_ENABLED_BY_DEFAULT;
 #else

ui/views/BUILD.gn

@@ -484,6 +484,7 @@ component("views") {
   deps = [
     "//base:i18n",
     "//base/third_party/dynamic_annotations",
+    "//build:chromeos_buildflags",
     "//cc/paint",
     "//mojo/public/cpp/bindings",
     "//skia",

ui/views/style/platform_style.cc

@@ -5,6 +5,7 @@
 #include "ui/views/style/platform_style.h"
 
 #include "build/build_config.h"
+#include "build/chromeos_buildflags.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/range/range.h"
 #include "ui/gfx/utf16_indexing.h"
@@ -16,7 +17,7 @@
 #include "ui/views/controls/focusable_border.h"
 #include "ui/views/controls/scrollbar/scroll_bar_views.h"
 
-#if defined(OS_CHROMEOS)
+#if defined(OS_CHROMEOS) || BUILDFLAG(IS_LACROS)
 #include "ui/views/controls/scrollbar/overlay_scroll_bar.h"
 #endif
 
@@ -53,7 +54,7 @@ const bool PlatformStyle::kInactiveWidgetControlsAppearDisabled = false;
 
 // static
 std::unique_ptr<ScrollBar> PlatformStyle::CreateScrollBar(bool is_horizontal) {
-#if defined(OS_CHROMEOS)
+#if defined(OS_CHROMEOS) || BUILDFLAG(IS_LACROS)
   return std::make_unique<OverlayScrollBar>(is_horizontal);
 #else
   return std::make_unique<ScrollBarViews>(is_horizontal);