Use the mojo::shell namespace consistently underly shell/.

shell/filename_util.cc

Index: shell/filename_util.cc
diff --git a/shell/filename_util.cc b/shell/filename_util.cc
index 8c1e8ae23a3a0b4c39e25f6f0ec7001bf264a49a..c1b901c5a825099119c0c1fd7ef05571b2cb681c 100644
--- a/shell/filename_util.cc
+++ b/shell/filename_util.cc
@@ -12,6 +12,7 @@
 #include "url/url_util.h"
 
 namespace mojo {
+namespace shell {
 
 // Prefix to prepend to get a file URL.
 static const base::FilePath::CharType kFileURLPrefix[] =
@@ -67,4 +68,5 @@ GURL AddTrailingSlashIfNeeded(const GURL& url) {
   return url.ReplaceComponents(replacements);
 }
 
+}  // namespace shell
 }  // namespace mojo