GitLab

Second attempt at landing. (See https://codereview.chromium.org/1586663006/)
Most gamepad code has been relocated to device/ since the original CL.

Reduces duplicate code between platform data fetchers by having things like
sanitation happen in the provider, and makes the data fetchers themselves more
modular. Data fetcher types can now be added and removed via the
GamepadDataFetcherManager.

BUG=577414

Review-Url: https://codereview.chromium.org/2129003002
Cr-Commit-Position: refs/heads/master@{#411375}