[Android]Don't check for child account/EDU device for every activity.
Extract a Forced Signin Processor out of FirstRun Signin Processor which
checks for child accounts and EDU device and is only triggered:
-Once per Chrome Application startup.
-On updates to accounts on the device.
Invariants:
FRE ToS checks and FRE pending signin checks still happen on every activity for now.
Dependent patchsets:
http://crrev.com/
1341423005
http://crrev.com/
1353393002
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=518830
Review URL: https://codereview.chromium.org/
1357643002
Cr-Commit-Position: refs/heads/master@{#350133}