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  * Centralizes rounded corner decoration, putting them on the window
    manager and adding a method to enable/disable as needed.

  * Add roundy corners to webviews, enabled on first webview and
    remove on destruction of final.

  * Add notification of color inversion to the window manager -- for
    accessibility to call into -- to invert the color of the rounded
    corners.

Bug: internal b/141369549
Test: manual
Change-Id: Ic0d6de3c718300add6f99b84b47a243bd5c74da3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1874059Reviewed-by: Daniel Nicoara <dnicoara@chromium.org>
Reviewed-by: Randy Rossi <rmrossi@chromium.org>
Commit-Queue: Ryan Daum <rdaum@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709142}