[Sync] Add SigninManagerWrapper in components/sync_driver.
The goal of this CL is to remove the chrome/ dependency many files
have on SupervisedUserSigninManagerWrapper, as we are moving sync
code into components/sync_driver. Since the concept of supervised
users does not yet exist in components/, this CL introduces a base
class, SigninManagerWrapper, which implements the default behavior.
chrome/ code will still use an actual SupervisedUserSigninManagerWrapper
object. I've converted the tests to use SigninManagerWrapper
instead to remove their chrome/ dependencies.
BUG=511246
Review URL: https://codereview.chromium.org/1306883010
Cr-Commit-Position: refs/heads/master@{#347170}
21 files changed
