Lock rotation when screen is manually rotated.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index e889131b95beca21793ddde3e57a98c6cf693080..374053c6dbc764cfcea343321abd6cfae74b6911 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -332,6 +332,11 @@ class ASH_EXPORT Shell : public SystemModalContainerEventFilterDelegate,
   // Test if the MaximizeModeWindowManager is enabled or not.
   bool IsMaximizeModeWindowManagerEnabled();
 
+  // Test if MaximizeModeWindowManager is not enabled, and if
+  // MaximizeModeController is not currently setting a display rotation. If
+  // true then changes to display settings can be saved.
+  bool ShouldSaveDisplaySettings();
+
   AcceleratorController* accelerator_controller() {
     return accelerator_controller_.get();
   }