Revert "Remove InputContentInfo#requestPermission()"

This reverts commit c4b8f36de5523366e354fc01b6cba81ad72f6423.

Having InputContentInfo#requestPermission() should not hurt developers,
but we can polish the behavior in a subsequent CL without changing
the API.

Bug: 29450031
Bug: 29892936
Change-Id: I1b43c19417b643d0c269af860db2d309b73a90d5
9 files changed