Cleanup the construction of app_list::SearchController.

After this CL, it can be moved to ui/app_list.

BUG=380875
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[email protected], [email protected]
TEST=no functional changes, build succeeds

Review URL: https://codereview.chromium.org/632083003

Cr-Commit-Position: refs/heads/master@{#298740}
10 files changed