Harmonize password sign-in promo.

* Separates the title from the promotion content (adds a secondary-style
  Label for body content).
* Removes the "no thanks" button (still present in the Cocoa version).

Bug: chromium:654115, chromium:654117
Change-Id: I83274934bfff8eaec6e5065233661ddd91447d39
Reviewed-on: https://chromium-review.googlesource.com/887726
Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Peter Boström <pbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532500}
6 files changed