Use Ash's ShelfWindowWatcher for app panel windows.

chrome/browser/media/webrtc/window_icon_util_chromeos.cc

Index: chrome/browser/media/webrtc/window_icon_util_chromeos.cc
diff --git a/chrome/browser/media/webrtc/window_icon_util_chromeos.cc b/chrome/browser/media/webrtc/window_icon_util_chromeos.cc
index 9c9130fafce47d08f45e7891f2b18b71084da2cb..530f013a30d7fd5c3c8f3074509224d4783fa0fe 100644
--- a/chrome/browser/media/webrtc/window_icon_util_chromeos.cc
+++ b/chrome/browser/media/webrtc/window_icon_util_chromeos.cc
@@ -14,8 +14,8 @@ gfx::ImageSkia GetWindowIcon(content::DesktopMediaID id) {
   if (!window)
     return gfx::ImageSkia();
 
-  const gfx::ImageSkia* icon_image_ptr =
-      window->GetProperty(aura::client::kWindowIconKey);
-
-  return icon_image_ptr ? *icon_image_ptr : gfx::ImageSkia();
+  gfx::ImageSkia* image = window->GetProperty(aura::client::kWindowIconKey);
+  if (!image)
+    image = window->GetProperty(aura::client::kAppIconKey);
+  return image ? *image : gfx::ImageSkia();
 }