Replace base::str[n]casecmp with helper functions.

base/files/file_path.cc

Index: base/files/file_path.cc
diff --git a/base/files/file_path.cc b/base/files/file_path.cc
index 92123533aaa55d1ec72eb72be873ed3bbd021340..d580c402b9d979b0779cf84c8f8f35450fabfc59 100644
--- a/base/files/file_path.cc
+++ b/base/files/file_path.cc
@@ -1263,12 +1263,7 @@ int FilePath::CompareIgnoreCase(StringPieceType string1,
 // TODO(rolandsteiner) check if this is sufficient/correct.
 int FilePath::CompareIgnoreCase(StringPieceType string1,
                                 StringPieceType string2) {
-  int comparison = strcasecmp(string1.data(), string2.data());
-  if (comparison < 0)
-    return -1;
-  if (comparison > 0)
-    return 1;
-  return 0;
+  return CompareCaseInsensitiveASCII(string1, string2);
 }
 
 #endif  // OS versions of CompareIgnoreCase()