Update the layout mode first when exiting tablet mode

ash/common/shell_observer.h

Index: ash/common/shell_observer.h
diff --git a/ash/common/shell_observer.h b/ash/common/shell_observer.h
index d65b9c3e37f589ac421c5c3266157ceb84644c52..facc29b9e2f289e6f2b7467ea49ebe413d625a70 100644
--- a/ash/common/shell_observer.h
+++ b/ash/common/shell_observer.h
@@ -60,7 +60,10 @@ class ASH_EXPORT ShellObserver {
   // animate though.
   virtual void OnMaximizeModeStarted() {}
 
-  // Called when the always maximize mode has ended. Windows may still be
+  // Called when the maximize mode is about to end.
+  virtual void OnMaximizeModeEnding() {}

[Mr4D (OOO till 08-26), 2017/02/21 16:17:18]

Sooner or later we should rename the "..MaximizeMode.." into something like
"..TabletMode.." since that is what it is. But that is something for another
refactor patch.

+
+  // Called when the maximize mode has ended. Windows may still be
   // animating but have been restored.
   virtual void OnMaximizeModeEnded() {}