Reapply 53892 with ARM build fix as suggested by Kobic.

For some reason, the ARM g++ thinks that comparing a pointer to a class
method against NULL is using NULL for arithemtic.  Switching to compare
against 0 makes this go away.  TODO added to investigate what is going on.

Original Review URL: http://codereview.chromium.org/3064009

TBR: hclam@chromium.org
BUG=50248
TEST=reproed locally with CodeSourcery g++ and verified change fixed things.

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@54083 0039d316-1c4b-4281-b951-d872f2087c98