[Accessibility] Add histograms for Mac/Windows reduce-motion APIs

These histograms will be used to guide the implementation of the CSS
prefers-reduced-motion media feature. The primary goal is to compare
usage levels across platforms. This CL starts with the two easiest
platforms to measure - Windows and MacOS.

Bug: 722548
Change-Id: I8643ec4df206e112f31943de0865b27775f72ce3
Reviewed-on: https://chromium-review.googlesource.com/c/1308104
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#605340}
3 files changed