Make *some* version of the Mac GN build work.

ui/base/BUILD.gn

Index: ui/base/BUILD.gn
diff --git a/ui/base/BUILD.gn b/ui/base/BUILD.gn
index dbef91dd79441948d0d38407b87041ba2fba754a..37a384965bf70650e37479c649cd58fe82ed9aba 100644
--- a/ui/base/BUILD.gn
+++ b/ui/base/BUILD.gn
@@ -683,6 +683,12 @@ source_set("test_support") {
       "ime/dummy_text_input_client.h",
     ]
   }
+
+  if (!use_aura) {
+    sources -= [
+      "test/ui_controls_aura.cc",
+    ]
+  }
 }
 
 if (is_android) {
@@ -865,6 +871,11 @@ test("ui_unittests") {
   }
 
   if (is_mac) {
+    sources -= [
+      "dragdrop/os_exchange_data_provider_aurax11_unittest.cc",
+      "x/selection_requestor_unittest.cc",
+    ]
+
     deps += [
       "//third_party/mozilla",
       #'ui_unittests_bundle',  TODO(GYP)