Revert r162691 "Fix for out-of-sync scale factor issue"

ash/display/multi_display_manager.cc

Index: ash/display/multi_display_manager.cc
diff --git a/ash/display/multi_display_manager.cc b/ash/display/multi_display_manager.cc
index e7fbf5edb0dc007c7f562974b4ec39e3d437b394..6df0887384e8c1b25d1adf9722440237cbef4638 100644
--- a/ash/display/multi_display_manager.cc
+++ b/ash/display/multi_display_manager.cc
@@ -317,9 +317,7 @@ const gfx::Display& MultiDisplayManager::GetDisplayNearestWindow(
     return DisplayController::GetPrimaryDisplay();
   const RootWindow* root = window->GetRootWindow();
   MultiDisplayManager* manager = const_cast<MultiDisplayManager*>(this);
-  return root ?
-      manager->FindDisplayForRootWindow(root) :
-      DisplayController::GetPrimaryDisplay();
+  return root ? manager->FindDisplayForRootWindow(root) : GetInvalidDisplay();
 }
 
 const gfx::Display& MultiDisplayManager::GetDisplayNearestPoint(