Extensions installed by policy overrun previously installed extensions.

chrome/browser/extensions/extension_service.cc

 // Copyright (c) 2011 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/extension_service.h"
 
 #include <algorithm>
 #include <set>
 
 #include "base/basictypes.h"
@@ skipping 397 matching lines @@
       linked_ptr<ExternalExtensionProviderInterface>(test_provider));
 }
 
 void ExtensionService::OnExternalExtensionUpdateUrlFound(
     const std::string& id,
     const GURL& update_url,
     Extension::Location location) {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   CHECK(Extension::IdIsValid(id));
 
-  if (GetExtensionById(id, true)) {
-    // Already installed.  Do not change the update URL that the extension set.
-    return;
+  const Extension* extension = GetExtensionById(id, true);
+  if (extension) {
+    // Already installed. Skip this install if the current location has
+    // higher priority than |location|.
+    Extension::Location current = extension->location();
+    if (current == Extension::GetHigherPriorityLocation(current, location))
+      return;
+    // Otherwise, overwrite the current installation.
   }
   pending_extension_manager()->AddFromExternalUpdateUrl(
       id, update_url, location);
   external_extension_url_added_ |= true;
 }
 
 bool ExtensionService::IsDownloadFromGallery(const GURL& download_url,
                                              const GURL& referrer_url) {
   // Special-case the themes mini-gallery.
   // TODO(erikkay) When that gallery goes away, remove this code.
@@ skipping 1725 matching lines @@
   OnExtensionInstalled(extension, false);  // Not from web store.
 }
 
 void ExtensionService::OnExtensionInstalled(
     const Extension* extension, bool from_webstore) {
   CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
 
   // Ensure extension is deleted unless we transfer ownership.
   scoped_refptr<const Extension> scoped_extension(extension);
   const std::string& id = extension->id();
-  bool initial_enable = !extension_prefs_->IsExtensionDisabled(id);
+  // Extensions installed by policy can't be disabled. So even if a previous
+  // installation disabled the extension, make sure it is now enabled.
+  bool initial_enable =
+      !extension_prefs_->IsExtensionDisabled(id) ||
+      !Extension::UserMayDisable(extension->location());
   PendingExtensionInfo pending_extension_info;
   if (pending_extension_manager()->GetById(id, &pending_extension_info)) {
     pending_extension_manager()->Remove(id);
 
     if (!pending_extension_info.ShouldAllowInstall(*extension)) {
       LOG(WARNING)
           << "ShouldAllowInstall() returned false for "
           << id << " of type " << extension->GetType()
           << " and update URL " << extension->update_url().spec()
           << "; not installing";
@@ skipping 411 matching lines @@
 
 ExtensionService::NaClModuleInfoList::iterator
     ExtensionService::FindNaClModule(const GURL& url) {
   for (NaClModuleInfoList::iterator iter = nacl_module_list_.begin();
        iter != nacl_module_list_.end(); ++iter) {
     if (iter->url == url)
       return iter;
   }
   return nacl_module_list_.end();
 }