Add ui_unittests to GN build.

ui/base/dragdrop/os_exchange_data_win_unittest.cc

Index: ui/base/dragdrop/os_exchange_data_win_unittest.cc
diff --git a/ui/base/dragdrop/os_exchange_data_win_unittest.cc b/ui/base/dragdrop/os_exchange_data_win_unittest.cc
index 36f235a959b6690996de3481acf87a147ebb01c1..1040ecfd279a6f2600b329403c94ec3c2a025f7e 100644
--- a/ui/base/dragdrop/os_exchange_data_win_unittest.cc
+++ b/ui/base/dragdrop/os_exchange_data_win_unittest.cc
@@ -66,7 +66,7 @@ TEST(OSExchangeDataWinTest, StringDataWritingViaCOM) {
   std::wstring title;
   EXPECT_TRUE(data2.GetURLAndTitle(
       OSExchangeData::CONVERT_FILENAMES, &url_from_data, &title));
-  GURL reference_url(in put);
+  GURL reference_url(input);
   EXPECT_EQ(reference_url.spec(), url_from_data.spec());
 }