embedding: add eutil::slice_to_str() convenience function

converts a *u8+length to &str and returns c_int

ports/cef/eutil.rs

@@ -2,6 +2,23 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use libc::c_int;
+use std::slice;
+use std::str;
+
 pub fn fptr_is_null(fptr: *const u8) -> bool {
     fptr.is_null()
 }
+
+pub fn slice_to_str(s: *const u8, l: uint, f: |&str| -> c_int) -> c_int {
+    unsafe {
+        slice::raw::buf_as_slice(s, l, |result| {
+             match str::from_utf8(result) {
+                  Some(ruststr) => {
+                       f(ruststr)
+                  },
+                  None => 0
+             }
+        })
+    }
+}