Exempt default apps from external-extension alerts.

BUG=106188
TEST=added


Review URL: http://codereview.chromium.org/8800016

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@113144 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/extensions/default_apps.cc b/chrome/browser/extensions/default_apps.cc
index fbd85fed..33ed772 100644
--- a/chrome/browser/extensions/default_apps.cc
+++ b/chrome/browser/extensions/default_apps.cc
@@ -114,6 +114,7 @@
                                     download_location, creation_flags),
       profile_(profile) {
   DCHECK(profile);
+  set_auto_acknowledge(true);
 }
 
 void Provider::VisitRegisteredExtension() {