Make FilePath accept FilePath as Append parameter.

base/file_path_unittest.cc

Index: base/file_path_unittest.cc
===================================================================
--- base/file_path_unittest.cc	(revision 6311)
+++ base/file_path_unittest.cc	(working copy)
@@ -273,9 +273,12 @@
   for (size_t i = 0; i < arraysize(cases); ++i) {
     FilePath root(cases[i].inputs[0]);
     FilePath::StringType leaf(cases[i].inputs[1]);
-    FilePath observed = root.Append(leaf);
-    EXPECT_EQ(FilePath::StringType(cases[i].expected), observed.value()) <<
+    FilePath observed_str = root.Append(leaf);
+    EXPECT_EQ(FilePath::StringType(cases[i].expected), observed_str.value()) <<
               "i: " << i << ", root: " << root.value() << ", leaf: " << leaf;
+    FilePath observed_path = root.Append(FilePath(leaf));
+    EXPECT_EQ(FilePath::StringType(cases[i].expected), observed_path.value()) <<
+              "i: " << i << ", root: " << root.value() << ", leaf: " << leaf;
   }
 }