Move shortcuts_database.{cc,h} to //chrome/browser/autocomplete

The sole client of ShortcutsDatabase is ShortcutsBackend and the
implementation of ShortcutsDatabase does not depends on //c/b/history
so it makes more sense to put this code in //c/b/autocomplete.

All files were moved using tools/git/move_source_files.py and then the
build system files (gyp and gn) were manually editted.

BUG=370850, 371538

Review URL: https://codereview.chromium.org/830503003

Cr-Commit-Position: refs/heads/master@{#309920}
8 files changed