Avoid memcmp on potentially unpacked structs in MailboxManager::TargetNameLess

Avoid memcmp on potentially unpacked structs in MailboxManager::TargetNameLess

R=piman@chromium.org

Committed: https://crrev.com/4f45409615609a5bf0084b9a7670b2fffda8a952
Cr-Commit-Position: refs/heads/master@{#293428}

[jamesr, 2014-09-04 23:23:30]

MailboxManager::Target name is just

struct {
  unsigned target;
  Mailbox mailbox;
};

and Mailbox is likely to need 8-byte alignment.  The c'tor doesn't try to zero
out any padding, if it exists.

[piman, 2014-09-04 23:38:00]

lgtm

[jamesr, 2014-09-04 23:41:01]

The CQ bit was checked by jamesr@chromium.org

[commit-bot: I haz the power, 2014-09-04 23:43:29]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/jamesr@chromium.org/538273002/1

[commit-bot: I haz the power, 2014-09-05 03:56:26]

Committed patchset #1 (id:1) as a796e41bbf7d85b47b934638ec2cefdc836fa16f

[commit-bot: I haz the power, 2014-09-10 03:36:29]

Patchset 1 (id:??) landed as
https://crrev.com/4f45409615609a5bf0084b9a7670b2fffda8a952
Cr-Commit-Position: refs/heads/master@{#293428}