Count All Cards for Explanatory Link Support

This change counts all cards indiscriminately for explanatory link
purposes. Previously, we only counted location cards.

BUG=340838

Review URL: https://codereview.chromium.org/154653003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250838 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250838