Correct the flag: is_extension_upgrade, which denote whether the extension is being upgrading.

chrome/browser/extensions/extension_service.cc

 // Copyright (c) 2013 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 <iterator>
 #include <set>
 
@@ skipping 1978 matching lines @@
   // default extension state to DISABLED when the --disable-extensions flag
   // is set (http://crbug.com/29067).
   if (!extensions_enabled() &&
       !extension->is_theme() &&
       extension->location() != Manifest::COMPONENT &&
       !Manifest::IsExternalLocation(extension->location())) {
     return;
   }
 
   bool is_extension_upgrade = false;
-  if (const Extension* old = GetInstalledExtension(extension->id())) {
-    is_extension_upgrade = true;
-    DCHECK_NE(extension, old);

[zhchbin, 2013/07/30 01:53:56]

As my comment, this DCHECK_NE make no sense because the AddExtension will be
called in many code path. This line of code is copied without check before it's
committed. So I also remove it. https://chromiumcodereview.appspot.com/14490002

+  const Extension* old = GetInstalledExtension(extension->id());
+  if (old) {
     // Other than for unpacked extensions, CrxInstaller should have guaranteed
     // that we aren't downgrading.
-    if (!Manifest::IsUnpackedLocation(extension->location()))
-      CHECK_GE(extension->version()->CompareTo(*(old->version())), 0);
+    if (!Manifest::IsUnpackedLocation(extension->location())) {
+      int version_compare_result =
+          extension->version()->CompareTo(*(old->version()));
+      is_extension_upgrade = version_compare_result > 0;
+      CHECK_GE(version_compare_result, 0);
+    }
   }
   SetBeingUpgraded(extension, is_extension_upgrade);
 
   // The extension is now loaded, remove its data from unloaded extension map.
   unloaded_extension_paths_.erase(extension->id());
 
   // If a terminated extension is loaded, remove it from the terminated list.
   UntrackTerminatedExtension(extension->id());
 
   // If the extension was disabled for a reload, then enable it.
@@ skipping 1054 matching lines @@
 }
 
 void ExtensionService::AddUpdateObserver(extensions::UpdateObserver* observer) {
   update_observers_.AddObserver(observer);
 }
 
 void ExtensionService::RemoveUpdateObserver(
     extensions::UpdateObserver* observer) {
   update_observers_.RemoveObserver(observer);
 }