API proposal for chrome.app.window to intercept all keys.

This API allows application like virtual desktop to obtain
all keys (including system keys like alt-tab). The
application will need "app.window.allKeys" for the API to
take effect. This API might not be supported in all platforms
(and it is not clear if it can be supported when the
application is not maximized in all platform either).

API proposal: http://goo.gl/O2Zzgh

BUG=166928

Review URL: https://codereview.chromium.org/297123002

Cr-Commit-Position: refs/heads/master@{#306219}
36 files changed