Blink CL https://codereview.chromium.org/879533003/ defines own
casts to convert between bridged types. The cast helpers in base
cannot be used in Blink. Fine tune the presubmit check to allow
for those by adding a negative look behind for reinterpret_cast.

BUG=

Review URL: https://codereview.chromium.org/1034523003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@294560 0039d316-1c4b-4281-b951-d872f2087c98