Don't update framebuffer_size to 0x0 when the framebuffer size didn't change.

ui/display/chromeos/update_display_configuration_task.cc

Index: ui/display/chromeos/update_display_configuration_task.cc
diff --git a/ui/display/chromeos/update_display_configuration_task.cc b/ui/display/chromeos/update_display_configuration_task.cc
index efa2d6d8bb63a79800c71ed4b4d42837d827f000..2db4422c3167964f13018215753d157ef3314274 100644
--- a/ui/display/chromeos/update_display_configuration_task.cc
+++ b/ui/display/chromeos/update_display_configuration_task.cc
@@ -86,8 +86,8 @@ void UpdateDisplayConfigurationTask::EnterState(
     callback.Run(ConfigureDisplaysTask::ERROR);
     return;
   }
-
   if (!requests.empty()) {
+    DCHECK(!framebuffer_size_.IsEmpty());
     delegate_->CreateFrameBuffer(framebuffer_size_);
     configure_task_.reset(
         new ConfigureDisplaysTask(delegate_, requests, callback));