Fix KeychainItemForForm so that it understands not to specify a path in case of Android credentials

Fix KeychainItemForForm so that it understands not to specify a path when looking for Keychain items corresponding to Android credentials.

While other code in PasswordStoreMac omitted the path before storing the Keychain item, KeychainItemForForm derived an erroneous path for an Android credential as well, and insisted to retrieve only Keychain items having that path -- yielding no matches. This has led to deleting and updating existing passwords not working.

BUG=476851
Committed: https://crrev.com/fe788235016d6087f6bcce24f7cab9147154e751
Cr-Commit-Position: refs/heads/master@{#325449}

[engedy, 2015-04-16 14:24:20]

engedy@chromium.org changed reviewers:
+ dconnelly@chromium.org

[engedy, 2015-04-16 14:54:22]

@Daniel, please take a look.

Caveat:

MockAppleKeychain::AddInternetPassword() does not normally care if newly added
element is a duplicate, it just adds it as a new element. There is an ugly hack
available to work around this and test the update code path in dependent code
(namely, in MacKeychainPasswordFormAdapter::AddPassword), but this requires
changing the mock in src/crypto/mock_apple_keychain_mac.cc, which I would prefer
not to do in this CL. I have left a TOOD and will do that in a follow-up CL.

Still, the fix to the update code path should be covered more-or-less, because
it was broken because of KeychainItemForForm(), and that is used in
HasPasswordExactlyMatchingForm(), which is now exercised in the tests for the
problematic inputs.

[dconnelly, 2015-04-16 15:07:11]

lgtm

[engedy, 2015-04-16 15:16:37]

The CQ bit was checked by engedy@chromium.org

[commit-bot: I haz the power, 2015-04-16 15:17:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1089233002/60001

[commit-bot: I haz the power, 2015-04-16 15:25:45]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-04-16 15:25:46]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromium_presub...)

[engedy, 2015-04-16 15:27:29]

engedy@chromium.org changed reviewers:
+ mkwst@chromium.org

[engedy, 2015-04-16 15:27:29]

@Mike, could you please review for OWNER's approval?

[Mike West, 2015-04-16 15:39:19]

The CQ bit was checked by mkwst@chromium.org

[Mike West, 2015-04-16 15:39:19]

lgtm

[commit-bot: I haz the power, 2015-04-16 15:39:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1089233002/60001

[commit-bot: I haz the power, 2015-04-16 15:59:54]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-04-16 16:01:02]

Patchset 4 (id:??) landed as
https://crrev.com/fe788235016d6087f6bcce24f7cab9147154e751
Cr-Commit-Position: refs/heads/master@{#325449}