DCHECK if any Bind*() calls occur after Step() has been called. The
bind cannot be implemented at that point, so most likely the calling
code has an error, such as a forgotted Reset().
Also DCHECK if Run() is called after Run() or Step() without an
intervening Reset(). Such a calling sequence is unlikely to be
intentional, because the results of calling Run() twice aren't
defined.
BUG=309759
Review URL: https://codereview.chromium.org/40733003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231098 0039d316-1c4b-4281-b951-d872f2087c98
097723df58