wm: Update namespace and header define guards.

src/platform/window_manager/panel.cc

Index: src/platform/window_manager/panel.cc
diff --git a/src/platform/window_manager/panel.cc b/src/platform/window_manager/panel.cc
index eb8f1204c2a0db7e611f14be6074dbc52c5a0c2b..24e8b988630b8744c74042991f4c27b897a85e88 100644
--- a/src/platform/window_manager/panel.cc
+++ b/src/platform/window_manager/panel.cc
@@ -24,7 +24,9 @@ DEFINE_int32(panel_max_height, -1,
              "Maximum height for panels (0 or less means unconstrained)");
 DEFINE_bool(panel_opaque_resize, false, "Resize panels opaquely");
 
-namespace chromeos {
+namespace window_manager {
+
+using chromeos::NewPermanentCallback;
 
 // Width of titlebars for collapsed panels.  Expanded panels' titlebars are
 // resized to match the width of the panel contents.
@@ -533,4 +535,4 @@ void Panel::ConfigureInputWindows() {
   }
 }
 
-}  // namespace chromeos
+}  // namespace window_manager