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

extensions/browser/extension_util.h

Index: extensions/browser/extension_util.h
diff --git a/extensions/browser/extension_util.h b/extensions/browser/extension_util.h
index 6bd3c86ea16c0bd69f8e97c351b2763f2c7755d6..b5f758edb1d226b3906bd3eb4f7eb481f5a3d786 100644
--- a/extensions/browser/extension_util.h
+++ b/extensions/browser/extension_util.h
@@ -14,7 +14,7 @@ class BrowserContext;
 }
 
 namespace extensions {
-
+class Extension;
 struct ExtensionInfo;
 
 namespace util {
@@ -40,6 +40,9 @@ bool HasIsolatedStorage(const ExtensionInfo& info);
 bool SiteHasIsolatedStorage(const GURL& extension_site_url,
                             content::BrowserContext* context);
 
+// Returns true if the extension can be enabled in incognito mode.
+bool CanBeIncognitoEnabled(const Extension* extension);
+
 }  // namespace util
 }  // namespace extensions