Prevent incognito windows from opening when incognito mode is disabled.

chrome/browser/extensions/extension_tabs_module_constants.cc

Index: chrome/browser/extensions/extension_tabs_module_constants.cc
diff --git a/chrome/browser/extensions/extension_tabs_module_constants.cc b/chrome/browser/extensions/extension_tabs_module_constants.cc
index 8c63750bc2a7a169e8e0cb765dd68969a0cf62fd..942235853b66a24c122bc406414180be76f0cb01 100644
--- a/chrome/browser/extensions/extension_tabs_module_constants.cc
+++ b/chrome/browser/extensions/extension_tabs_module_constants.cc
@@ -75,6 +75,8 @@ const char kTabStripNotEditableError[] =
 const char kNoSelectedTabError[] = "No selected tab";
 const char kNoHighlightedTabError[] = "No highlighted tab";
 const char kIncognitoModeIsDisabled[] = "Incognito mode is disabled.";
+const char kIncognitoModeIsForced[] = "Incognito mode is forced. "
+    "Cannot open normal windows.";
 const char kURLsNotAllowedInIncognitoError[] = "Cannot open URL \"*\" "
     "in an incognito window.";
 const char kInvalidUrlError[] = "Invalid url: \"*\".";