Rename MacKeychain to AppleKeychain
Rename MacKeychain to AppleKeychain and add mac and iOS specific
implementations (crypto/apple_keychain_ios.mm and
crypto/apple_keychain_mac.mm). Rename MockKeychain to
MockAppleKeychain and split its implementations in 3 files
crypto/mock_apple_keychain.cc, crypto/mock_apple_keychain_ios.cc and
crypto/mock_apple_keychain_mac.cc).
Review URL: https://chromiumcodereview.appspot.com/
10875029
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@154123 0039d316-1c4b-4281-b951-d872f2087c98