Delete callbacks after use in canned browsing data helpers.

BUG=49750
TEST=Canned*.*

Review URL: http://codereview.chromium.org/3178001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@55688 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/browsing_data_appcache_helper.cc b/chrome/browser/browsing_data_appcache_helper.cc
index 2e58c6b..66f9b79 100644
--- a/chrome/browser/browsing_data_appcache_helper.cc
+++ b/chrome/browser/browsing_data_appcache_helper.cc
@@ -130,4 +130,5 @@
 void CannedBrowsingDataAppCacheHelper::StartFetching(
     Callback0::Type* completion_callback) {
   completion_callback->Run();
+  delete completion_callback;
 }