[Extensions UI] Fix a bug in the extension message bubbles

chrome/browser/ui/cocoa/extensions/extension_message_bubble_browsertest_mac.mm

Index: chrome/browser/ui/cocoa/extensions/extension_message_bubble_browsertest_mac.mm
diff --git a/chrome/browser/ui/cocoa/extensions/extension_message_bubble_browsertest_mac.mm b/chrome/browser/ui/cocoa/extensions/extension_message_bubble_browsertest_mac.mm
index f5997715f8940ade82f144de9c2385595e09fc8a..e7dd1a813be14848bf3cae7baa4d26a3422f0755 100644
--- a/chrome/browser/ui/cocoa/extensions/extension_message_bubble_browsertest_mac.mm
+++ b/chrome/browser/ui/cocoa/extensions/extension_message_bubble_browsertest_mac.mm
@@ -152,3 +152,8 @@ IN_PROC_BROWSER_TEST_F(ExtensionMessageBubbleBrowserTestMac,
                        TestUninstallDangerousExtension) {
   TestUninstallDangerousExtension();
 }
+
+IN_PROC_BROWSER_TEST_F(ExtensionMessageBubbleBrowserTestMac,
+                       TestDevModeBubbleIsntShownTwice) {
+  TestDevModeBubbleIsntShownTwice();
+}