Adds support for mojo apps to live in their own directory

mojo/shell/filename_util.h

Index: mojo/shell/filename_util.h
diff --git a/mojo/shell/filename_util.h b/mojo/shell/filename_util.h
index 28d0e780a9910576e031f0b578d81318a152277e..31aba797eb33b0aaf7a928916fae206bc190095d 100644
--- a/mojo/shell/filename_util.h
+++ b/mojo/shell/filename_util.h
@@ -22,6 +22,9 @@ GURL FilePathToFileURL(const base::FilePath& path);
 // slash so that GURL.Resolve(...) works correctly.
 GURL AddTrailingSlashIfNeeded(const GURL& url);
 
+// Converts a file url to a path
+base::FilePath UrlToFilePath(const GURL& url);
+
 }  // namespace shell
 }  // namespace mojo