chromeos: Turn off displays on suspend

ui/display/types/native_display_delegate.h

Index: ui/display/types/native_display_delegate.h
diff --git a/ui/display/types/native_display_delegate.h b/ui/display/types/native_display_delegate.h
index b17be8f1cffda92a19ad1e77a6591bd75486a8dc..7acf8ad65178541c40c88341484d9d9ad09e1a9a 100644
--- a/ui/display/types/native_display_delegate.h
+++ b/ui/display/types/native_display_delegate.h
@@ -68,6 +68,11 @@ class DISPLAY_TYPES_EXPORT NativeDisplayDelegate {
   // Enables DPMS and forces it to the "on" state.
   virtual void ForceDPMSOn() = 0;
 
+  // Queries for a list of cached displays and returns them via |callback|.
+  // Note that the list of displays may be outdated, so this should not be
+  // solely relied upon for correctness.
+  virtual void GetCachedDisplays(const GetDisplaysCallback& callback) = 0;
+
   // Queries for a list of fresh displays and returns them via |callback|.
   // Note the query operation may be expensive and take over 60 milliseconds.
   virtual void GetDisplays(const GetDisplaysCallback& callback) = 0;