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This CL adds a new histogram enum GAMEPAD_INTERACTION to
Arc.UserInteraction, which will be recorded on the first time a user
sends a gamepad event to an ARC++ app window. It resets every time the
window is deactivated.

This will be used as success metrics of ARC Improved Gamepad project
go/arc-improved-gamepad.

TEST=manual(Press gamepad buttons when an ARC++ app is active and check
chrome://histograms)
BUG=b:130597086

Change-Id: I90c4d00399a7227a102ebd9e81861b735bef6001
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1605667
Commit-Queue: Tetsui Ohkubo <tetsui@chromium.org>
Reviewed-by: Kevin Schoedel <kpschoedel@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Reviewed-by: Maajid <maajid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659665}