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1) Add a ManageMigrationUiController above
LocalCardMigration(Bubble/Dialog)ControllerImpl to control the entire
flow and what ui to show. Also it makes easier to interact with
LocalCardMigrationIconView and it keeps ChromeAutofillClient cleaner.

2) Separate LocalCardMigrationFlowStep from LocalCardMigrationDialogState,
the previous one is the enum for ManageMigrationUiController to decide
what to do while the latter one is a pure view state for dialog.

Upload screenshots for what the flow should be like in the
bug (comment#15).

Bug: 897998
Change-Id: I79f3b491f6ab86b204f05d53cda7fe9bd737d28e
Reviewed-on: https://chromium-review.googlesource.com/c/1328146
Commit-Queue: Siyu An <siyua@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Reviewed-by: Evan Stade <estade@chromium.org>
Reviewed-by: Jared Saul <jsaul@google.com>
Cr-Commit-Position: refs/heads/master@{#608525}