Add a group policy controlling which sites can install extensions.

chrome/browser/extensions/crx_installer.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/extensions/crx_installer.h"
 
 #include <map>
 #include <set>
 
 #include "base/bind.h"
@@ skipping 80 matching lines @@
       extensions_enabled_(frontend_weak->extensions_enabled()),
       delete_source_(false),
       create_app_shortcut_(false),
       frontend_weak_(frontend_weak),
       profile_(frontend_weak->profile()),
       client_(client),
       apps_require_extension_mime_type_(false),
       allow_silent_install_(false),
       install_cause_(extension_misc::INSTALL_CAUSE_UNSET),
       creation_flags_(Extension::NO_FLAGS),
-      allow_off_store_install_(false) {
+      off_store_install_allow_reason_(OffStoreInstallDisallowed) {
   if (!approval)
     return;
 
   CHECK(profile_->IsSameProfile(approval->profile));
   client_->install_ui()->SetUseAppInstalledBubble(
       approval->use_app_installed_bubble);
   client_->install_ui()->SetSkipPostInstallUI(approval->skip_post_install_ui);
 
   if (approval->skip_install_dialog) {
     // Mark the extension as approved, but save the expected manifest and ID
@@ skipping 141 matching lines @@
                                   NumOffStoreInstallDecision);
       } else {
         UMA_HISTOGRAM_ENUMERATION(kHistogramName, OffStoreInstallAllowed,
                                   NumOffStoreInstallDecision);
       }
     } else {
       const char* kHistogramName = "Extensions.OffStoreInstallDecisionHard";
       if (is_gallery_install()) {
         UMA_HISTOGRAM_ENUMERATION(kHistogramName, OnStoreInstall,
                                   NumOffStoreInstallDecision);
-      } else if (allow_off_store_install_) {
+      } else if (off_store_install_allow_reason_ != OffStoreInstallDisallowed) {
         UMA_HISTOGRAM_ENUMERATION(kHistogramName, OffStoreInstallAllowed,
                                   NumOffStoreInstallDecision);
+        UMA_HISTOGRAM_ENUMERATION("Extensions.OffStoreInstallAllowReason",
+                                  off_store_install_allow_reason_,
+                                  NumOffStoreInstallAllowReasons);
       } else {
         UMA_HISTOGRAM_ENUMERATION(kHistogramName, OffStoreInstallDisallowed,
                                   NumOffStoreInstallDecision);
         *error = l10n_util::GetStringUTF16(
             IDS_EXTENSION_INSTALL_DISALLOWED_ON_SITE);
         return false;
       }
     }
   }
 
@@ skipping 321 matching lines @@
   // Some users (such as the download shelf) need to know when a
   // CRXInstaller is done.  Listening for the EXTENSION_* events
   // is problematic because they don't know anything about the
   // extension before it is unpacked, so they cannot filter based
   // on the extension.
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_CRX_INSTALLER_DONE,
       content::Source<CrxInstaller>(this),
       content::Details<const Extension>(extension));
 }