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..9a0d9de3380c6b3fc9c5fbfa98ac083e0501534a 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1340,9 +1340,15 @@ 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.

[Yoyo Zhou, 2012/06/07 19:19:15]

Should this say "this is controlled by the administrator" like the two below?

[Aaron Boodman, 2012/06/07 22:37:11]

The ones below aren't strictly true. I mean anyone can set the pref, if they
edit the file. I don't think it makes sense to mention the administrator here...
that's a separate system. I'll just remove it from the other two.

+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.
 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