Add a group policy controlling which sites can install extensions.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 19ba435b4873620c2aa68295a55315da30164575..da3499d9d97c07f77066ede906b21a0e6b2603b5 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1340,13 +1340,18 @@ const char kDisablePluginFinder[] = "plugins.disable_plugin_finder";
 const char kBrowserActionContainerWidth[] =
     "extensions.browseractions.container.width";
 
+// The sites that are allowed to install extensions. These sites should be
+// allowed to install extensions without the scary dangerous downloads bar.
+// Also, when off-store-extension installs are disabled, these sites are exempt.
+const char kExtensionAllowedInstallSites[] = "extensions.allowed_install_sites";
+
 // A whitelist of extension ids the user can install: exceptions from the
-// following blacklist. This is controlled by the administrator.
+// following blacklist.
 const char kExtensionInstallAllowList[] = "extensions.install.allowlist";
+
 // A blacklist, containing extensions the user cannot install. This list can
-// conatin "*" meaning all extensions. This is controlled by the administrator.
-// This list should not be confused with the extension blacklist, which is
-// Google controlled.
+// conatin "*" meaning all extensions. This list should not be confused with the

[Mattias Nissler (ping if slow), 2012/06/08 09:38:22]

nit: s/conatin/contain/

+// extension blacklist, which is Google controlled.
 const char kExtensionInstallDenyList[] = "extensions.install.denylist";
 
 // Whether we have run the extension-alert system (see ExtensionGlobalError)