[Blimp client] Move client code into blimp::client namespace

blimp/client/session/navigation_feature.cc

Index: blimp/client/session/navigation_feature.cc
diff --git a/blimp/client/session/navigation_feature.cc b/blimp/client/session/navigation_feature.cc
index 2b9bf0a58a5ad88f75f31856ba7826b3aa3f202b..bafd6335b94b58eac48dda10a02f9826779881ce 100644
--- a/blimp/client/session/navigation_feature.cc
+++ b/blimp/client/session/navigation_feature.cc
@@ -11,6 +11,7 @@
 #include "url/gurl.h"
 
 namespace blimp {
+namespace client {
 
 NavigationFeature::NavigationFeature() {}
 
@@ -130,4 +131,5 @@ NavigationFeature::NavigationFeatureDelegate* NavigationFeature::FindDelegate(
   return nullptr;
 }
 
+}  // namespace client
 }  // namespace blimp