Automatically redraw the display on resume.

services/surfaces/surfaces_scheduler.cc

Index: services/surfaces/surfaces_scheduler.cc
diff --git a/services/surfaces/surfaces_scheduler.cc b/services/surfaces/surfaces_scheduler.cc
index b5edb05d43a4e636502fa440c19313e5277868c6..1a236206d1cd4663487243b71c5c4d84aca333ae 100644
--- a/services/surfaces/surfaces_scheduler.cc
+++ b/services/surfaces/surfaces_scheduler.cc
@@ -37,6 +37,10 @@ void SurfacesScheduler::OnVSyncParametersUpdated(base::TimeTicks timebase,
 void SurfacesScheduler::AddDisplay(cc::Display* display) {
   DCHECK(displays_.find(display) == displays_.end());
   displays_.insert(display);
+
+  // A draw might be necessary (e.g., this display might be getting added on
+  // resumption from backgrounding).
+  SetNeedsDraw();
 }
 
 void SurfacesScheduler::RemoveDisplay(cc::Display* display) {