Move passphrase dialog logic to the enum.

Move passphrase dialog logic to the enum.

In preparation for a bug fix.

BUG=419927
TBR=zea@chromium.org
Review URL: https://codereview.chromium.org/642623002

Cr-Commit-Position: refs/heads/master@{#298900}
(cherry picked from commit cd77acb3d1dc9c4f5e813b6f8239915b06a6cdde)

Committed: https://chromium.googlesource.com/chromium/src/+/f7a0305e02b34300e4441b3d7da342cda040c919

[nyquist, 2014-10-22 21:41:14]

nyquist@chromium.org changed reviewers:
+ zea@chromium.org

[nyquist, 2014-10-22 21:41:15]

zea: FYI

[nyquist, 2014-10-22 21:42:56]

Committed patchset #1 (id:1) manually as
f7a0305e02b34300e4441b3d7da342cda040c919 (presubmit successful).