GitLab

Originally only sysex permission requests are exposed to the
content layer, but with this series of patches, all Web MIDI requests
will be exposed to the content layer so that each chromium embedder
can decide how to decide several permissions.

First of all, expose all requests outside Blink.
Changes for the permission service will follow as a separate patch.

BUG=535181

Review URL: https://codereview.chromium.org/1602703005

Cr-Commit-Position: refs/heads/master@{#372044}