Split kPasswordImportExport feature into two

While importing and exporting of passwords are closely related, the
two features are to a significant extent independent, as is their
development. In particular, the export feature has its own merits even
in the temporary absence of the importing counterpart.

To allow flexible scheduling of work and launching of the different
parts in different milestones, the existing kPasswordImportExport
feature is gettign split into two, one for import, one for export.

Bug: 341477
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: I45afd96a83f1a8d70d80331971f6da9a5683a2ca
Reviewed-on: https://chromium-review.googlesource.com/765827
Reviewed-by: Steven Bennetts <[email protected]>
Reviewed-by: Christos Froussios <[email protected]>
Commit-Queue: Vaclav Brozek <[email protected]>
Cr-Commit-Position: refs/heads/master@{#517079}
9 files changed