ChildAccountService[Java] delegates everything to native side.
Most of the child account detection/enforcement logic has been divided amongst
the ChildAccountInfoFetcher and ForcedSigninProcessor.
ForcedSigninProcessor will make sure that child accounts are detected and
are signed in.
ChildAccountInfoFetcher only activates on signin and informs the
native ChildAccountService about the child account and takes responsiblity for
any further updates (graduation) or account changes.
Depends on http://crrev.com/
1357643002
Dependent patchset http://crrev.com/
1353393002
BUG=518830
Review URL: https://codereview.chromium.org/
1341423005
Cr-Commit-Position: refs/heads/master@{#350138}