Change ContentSettingsType's scoping type and hookup migration code

This is a follow up CL of https://codereview.chromium.org/1895993003/ and
https://codereview.chromium.org/2078893002/.

In this CL, the scoping type of content setting types are changed to origin
scoped so that new settings generated for these types affect origins only.
Also migration code is brought to take effect to deal with old domain scoped
settings.

BUG=604612

Review-Url: https://codereview.chromium.org/2075103002
Cr-Commit-Position: refs/heads/master@{#408067}
9 files changed