Place primary screen before secondary screens in picker

chrome/browser/media/desktop_media_list_ash.cc

Index: chrome/browser/media/desktop_media_list_ash.cc
diff --git a/chrome/browser/media/desktop_media_list_ash.cc b/chrome/browser/media/desktop_media_list_ash.cc
index ac88e0d6710952468270510ed64e2cc96f406148..b6fd3d3d92a6fad41513dc955a68f79b42217b4b 100644
--- a/chrome/browser/media/desktop_media_list_ash.cc
+++ b/chrome/browser/media/desktop_media_list_ash.cc
@@ -180,7 +180,11 @@ void DesktopMediaListAsh::EnumerateSources(
     if (source_types_ & SCREENS) {
       SourceDescription screen_source(
           content::DesktopMediaID::RegisterAuraWindow(*iter), (*iter)->title());
-      sources->push_back(screen_source);
+      if (*iter == ash::Shell::GetPrimaryRootWindow()) {
+        sources->insert(sources->begin(), screen_source);
+      } else {
+        sources->push_back(screen_source);
+      }
 
       CaptureThumbnail(screen_source.id, *iter);
     }