Add a unit test that filenames aren't unintentionally converted to URLs.

ui/base/dragdrop/os_exchange_data_provider_win.cc

Index: ui/base/dragdrop/os_exchange_data_provider_win.cc
diff --git a/ui/base/dragdrop/os_exchange_data_provider_win.cc b/ui/base/dragdrop/os_exchange_data_provider_win.cc
index 4cbfa4a8512d2904c6ae090db90bd1dfb4a2e9b0..729269c12ce6573c3d549614aaa712ecc78209ff 100644
--- a/ui/base/dragdrop/os_exchange_data_provider_win.cc
+++ b/ui/base/dragdrop/os_exchange_data_provider_win.cc
@@ -411,15 +411,12 @@ bool OSExchangeDataProviderWin::GetURLAndTitle(
   base::string16 url_str;
   bool success = ClipboardUtil::GetUrl(
       source_object_,
-      &url_str,
+      url,
       title,
       policy == OSExchangeData::CONVERT_FILENAMES ? true : false);
   if (success) {
-    GURL test_url(url_str);
-    if (test_url.is_valid()) {
-      *url = test_url;
-      return true;
-    }
+    DCHECK(url->is_valid());
+    return true;
   } else if (GetPlainTextURL(source_object_, url)) {
     if (url->is_valid())
       *title = net::GetSuggestedFilename(*url, "", "", "", "", std::string());