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This CL moves the GetPickerAction and GetDestinationPlatform function
calls out of RecordUma such that ChromeOSAppsNavigationThrottle can
call its own GetDestinationPlatform which sets the platform for when
a preferred activity is found.

BUG=968411

Change-Id: Ia838828ec4d03f1543243827f87601bfa2534c4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1836293
Commit-Queue: Melissa Zhang <melzhang@chromium.org>
Reviewed-by: Maggie Cai <mxcai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#702730}