[SystemDisplayAPI] Observe display change on linux/win/mac as well

chrome/browser/extensions/display_info_provider_aura.cc

Index: chrome/browser/extensions/display_info_provider_aura.cc
diff --git a/chrome/browser/extensions/display_info_provider_aura.cc b/chrome/browser/extensions/display_info_provider_aura.cc
index bcf0e20c89a10860f6d8c716ef5e6ad19cd43243..bf9a952b45b0fa5d2485db62d8ea51b703540095 100644
--- a/chrome/browser/extensions/display_info_provider_aura.cc
+++ b/chrome/browser/extensions/display_info_provider_aura.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/extensions/display_info_provider_aura.h"
 
+#include "ui/gfx/screen.h"
+
 namespace extensions {
 
 DisplayInfoProviderAura::DisplayInfoProviderAura() {
@@ -27,7 +29,7 @@ void DisplayInfoProviderAura::UpdateDisplayUnitInfoForPlatform(
 }
 
 gfx::Screen* DisplayInfoProviderAura::GetActiveScreen() {
-  return NULL;
+  return gfx::Screen::GetNativeScreen();
 }
 
 // static