Adding experimental maximize mode (behind a flag)

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index 92ef58cc91fe7c3fc08f9c526f8a5e24afdf232a..43ee1c624cf6fb6e8186428d95ed1ca6320477ce 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -200,6 +200,10 @@ class ASH_EXPORT Shell
   // True if "launcher per display" feature  is enabled.
   static bool IsLauncherPerDisplayEnabled();
 
+  // True if an experimental maximize mode is enabled which forces browser and
+  // application windows to be maximized only.
+  static bool IsForcedMaximizeMode();
+
   void set_active_root_window(aura::RootWindow* active_root_window) {
     active_root_window_ = active_root_window;
   }