Draw nicer arrows when the scrollbar buttons are not square.

ui/native_theme/BUILD.gn

Index: ui/native_theme/BUILD.gn
diff --git a/ui/native_theme/BUILD.gn b/ui/native_theme/BUILD.gn
index fbe42371ce901615092026b78a3692a9a26238d2..b79e1131c2a6130c8c6db74ee99af5791b225007 100644
--- a/ui/native_theme/BUILD.gn
+++ b/ui/native_theme/BUILD.gn
@@ -3,6 +3,7 @@
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
+import("//testing/test.gni")
 
 component("native_theme") {
   sources = [
@@ -62,3 +63,24 @@ component("native_theme") {
     ]
   }
 }
+
+test("native_theme_unittests") {
+  sources = []
+
+  if (use_aura) {
+    sources += [ "native_theme_aura_unittest.cc" ]
+  }
+
+  if (is_mac) {
+    sources += [ "native_theme_mac_unittest.cc" ]
+  }
+
+  deps = [
+    ":native_theme",
+    "//base/test:run_all_unittests",
+    "//base/test:test_support",
+    "//skia:skia",
+    "//testing/gtest",
+    "//ui/gfx/geometry:geometry",
+  ]
+}