DRT should handle relative path arguments.

webkit/support/webkit_support.cc

Index: webkit/support/webkit_support.cc
diff --git a/webkit/support/webkit_support.cc b/webkit/support/webkit_support.cc
index 97b963d03d45be91e4c3c9cb6050038e09918296..16e277f7832901812c73270d170851649172201c 100644
--- a/webkit/support/webkit_support.cc
+++ b/webkit/support/webkit_support.cc
@@ -636,10 +636,12 @@ WebURL CreateURLForPathOrURL(const std::string& path_or_url_in_nativemb) {
   if (url.is_valid() && url.has_scheme())
     return WebURL(url);
 #if defined(OS_WIN)
-  return net::FilePathToFileURL(FilePath(wide_path_or_url));
+  FilePath path(wide_path_or_url);
 #else
-  return net::FilePathToFileURL(FilePath(path_or_url_in_nativemb));
+  FilePath path(path_or_url_in_nativemb);
 #endif
+  file_util::AbsolutePath(&path);
+  return net::FilePathToFileURL(path);
 }
 
 WebURL RewriteLayoutTestsURL(const std::string& utf8_url) {