Added the "Show as Tab" option for popups on OSX

chrome/browser/app_controller_mac.mm

Index: chrome/browser/app_controller_mac.mm
diff --git a/chrome/browser/app_controller_mac.mm b/chrome/browser/app_controller_mac.mm
index d9eceb7e699a1c6e103afbc9eb876896ca1e2c0a..e33ff8e3294d57c921d74ea0a51bcdfeb029d68e 100644
--- a/chrome/browser/app_controller_mac.mm
+++ b/chrome/browser/app_controller_mac.mm
@@ -982,6 +982,16 @@ class AppControllerProfileObserver : public ProfileInfoCacheObserver {
                    ![self keyWindowIsModal] : NO;
       }
     }
+
+    // "Show as tab" should only appear when the current window is a popup.
+    // Since |validateUserInterfaceItem:| is called only when there are no
+    // key windows, we should just hide this.
+    // This is handled outside of the switch statement because we want to hide
+    // this regardless if the command is supported or not.
+    if (tag == IDC_SHOW_AS_TAB) {
+      NSMenuItem* menuItem = base::mac::ObjCCast<NSMenuItem>(item);
+      [menuItem setHidden:YES];
+    }
   } else if (action == @selector(terminate:)) {
     enable = YES;
   } else if (action == @selector(showPreferences:)) {