Switch default WM mode to managed

ash/shell.cc

Index: ash/shell.cc
diff --git a/ash/shell.cc b/ash/shell.cc
index 2dbdafcf5e560035fdc86d3e55c1beac2fb06f7e..d884c629730928743dacdf42338eaa8c4cea6fd8 100644
--- a/ash/shell.cc
+++ b/ash/shell.cc
@@ -248,7 +248,7 @@ Shell::Shell(ShellDelegate* delegate)
 #endif
       delegate_(delegate),
       shelf_(NULL),
-      window_mode_(MODE_OVERLAPPING),
+      window_mode_(MODE_MANAGED),
       desktop_background_mode_(BACKGROUND_IMAGE),
       root_window_layout_(NULL),
       status_widget_(NULL) {
@@ -445,8 +445,8 @@ Shell::WindowMode Shell::ComputeWindowMode(CommandLine* command_line) const {
       return MODE_OVERLAPPING;
   }
 
-  // Overlapping is the default.
-  return Shell::MODE_OVERLAPPING;
+  // Managed is the default.
+  return Shell::MODE_MANAGED;
 }
 
 aura::Window* Shell::GetContainer(int container_id) {