Support using TrackedCallbacks as hints to determine the handling thread of resource reply messages.

BUG=269737
TEST=None

Review URL: https://codereview.chromium.org/46433002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240282 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 240282