Allow non-absolute path for variables. This fixes grit to do variable

tools/grit/grit/grd_reader_unittest.py

Index: tools/grit/grit/grd_reader_unittest.py
diff --git a/tools/grit/grit/grd_reader_unittest.py b/tools/grit/grit/grd_reader_unittest.py
index 050f877c4bc876948e4efce6bfb329f0f9749047..f922a976a827d5ecb4b894bac9146fdade3621d5 100644
--- a/tools/grit/grit/grd_reader_unittest.py
+++ b/tools/grit/grit/grd_reader_unittest.py
@@ -146,9 +146,10 @@ class GrdReaderUnittest(unittest.TestCase):
     grit_root_dir = os.path.join(os.path.abspath(os.path.dirname(__file__)),
                                  '..')
     root.AssignFirstIds(
-        # This file does not actually exist, but the path must match
-        # the path of the resource_ids file as it has SRCDIR set to "."
-        os.path.join(grit_root_dir, "grit/testdata/test.grd"),
+        # This file does not actually exist, but must use absolute
+        # path as resource_ids has '' for SRCDIR (see special handling
+        # in grit.node.misc).
+        os.path.join(grit_root_dir, "/test.grd"),
         os.path.join(grit_root_dir, "grit/testdata/resource_ids"),
         {})
     messages_node = root.children[0].children[0]