Added a module for the Presentation API implementation and a dummy navigator.presentation.onavailablechange IDL.

BUG=412331

Intent to implement on blink-dev: https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/J0ToSdOQVP8

Review URL: https://codereview.chromium.org/408663002

git-svn-id: svn://svn.chromium.org/blink/trunk@181975 bbb929c8-8fbe-4397-9dbb-9b2b20218538