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
Review URL: https://codereview.chromium.org/
1089233002
Cr-Commit-Position: refs/heads/master@{#325449}