Allow extensions to specify that they are not allowed in incognito mode.

extensions/common/manifest_constants.cc

Index: extensions/common/manifest_constants.cc
diff --git a/extensions/common/manifest_constants.cc b/extensions/common/manifest_constants.cc
index 6dd9a4126bda0f822cbbdbedbcdf3b0a034ea631..5d9ea2d8086675e33473fc2c08f9cbe67e6ad43a 100644
--- a/extensions/common/manifest_constants.cc
+++ b/extensions/common/manifest_constants.cc
@@ -195,6 +195,7 @@ namespace manifest_values {
 
 const char kApiKey[] = "api_key";
 const char kBrowserActionCommandEvent[] = "_execute_browser_action";
+const char kIncognitoNotAllowed[] = "not_allowed";
 const char kIncognitoSplit[] = "split";
 const char kIncognitoSpanning[] = "spanning";
 const char kIsolatedStorage[] = "storage";