OK, here's john's patch plus my sync stuff.

chrome/browser/ui/panels/panel_extension_browsertest.cc

Index: chrome/browser/ui/panels/panel_extension_browsertest.cc
diff --git a/chrome/browser/ui/panels/panel_extension_browsertest.cc b/chrome/browser/ui/panels/panel_extension_browsertest.cc
index 34277a42f2e3cd12cb1b45188d563d2dc63bcfd0..6f4a56a16c1da3f6d3b33eff7228a8af424d14ba 100644
--- a/chrome/browser/ui/panels/panel_extension_browsertest.cc
+++ b/chrome/browser/ui/panels/panel_extension_browsertest.cc
@@ -101,8 +101,15 @@ IN_PROC_BROWSER_TEST_F(PanelExtensionBrowserTest, PanelAppIcon) {
 
 // Tests that icon loading might not be completed when the panel is closed.
 // (crbug.com/151484)
+//
+// TODO(linux_aura) http://crbug.com/163931
+#if defined(OS_LINUX) && !defined(OS_CHROMEOS) && defined(USE_AURA)
+#define MAYBE_ClosePanelBeforeIconLoadingCompleted DISABLED_ClosePanelBeforeIconLoadingCompleted
+#else
+#define MAYBE_ClosePanelBeforeIconLoadingCompleted ClosePanelBeforeIconLoadingCompleted
+#endif
 IN_PROC_BROWSER_TEST_F(PanelExtensionBrowserTest,
-                       ClosePanelBeforeIconLoadingCompleted) {
+                       MAYBE_ClosePanelBeforeIconLoadingCompleted) {
   const Extension* extension =
       LoadExtension(test_data_dir_.AppendASCII("test_extension"));
   Panel* panel = CreatePanelFromExtension(extension);