Remove remaining legacy SplitString calls.

tools/gn/command_refs.cc

Index: tools/gn/command_refs.cc
diff --git a/tools/gn/command_refs.cc b/tools/gn/command_refs.cc
index 961e2102c8fa851be622f9a5faa3659d85a1934d..742b43b350338652429fdd0fad767718ed6fb877 100644
--- a/tools/gn/command_refs.cc
+++ b/tools/gn/command_refs.cc
@@ -408,7 +408,6 @@ int RunRefs(const std::vector<std::string>& args) {
     if (args[i][0] == '@') {
       // The argument is as a path to a response file.
       std::string contents;
-      std::vector<std::string> lines;
       bool ret = base::ReadFileToString(UTF8ToFilePath(args[i].substr(1)),
                                         &contents);
       if (!ret) {
@@ -416,8 +415,8 @@ int RunRefs(const std::vector<std::string>& args) {
             .PrintToStdout();
         return 1;
       }
-      base::SplitString(contents, '\n', &lines);
-      for (const auto& line : lines) {
+      for (const std::string& line : base::SplitString(
+               contents, "\n", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL)) {
         if (!line.empty())
           inputs.push_back(line);
       }