Mark MediaDevices-related interfaces as SecureContext

This CL marks the following as SecureContext:
* mediaDevices field of the Navigator interface
* getUserMedia method of the Navigator interface (including prefixed version)
* MediaDevices interface
* MediaDeviceInfo interface

This effectively makes getUserMedia(), getDisplayMedia() and
enumerateDevices() available only on secure contexts.

Intent to Remove thread:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/SGWYHfR5CyY

Bug: 927230
Change-Id: I6f5672dcaae22a1744ade2b913aae29e75ddcc9b
Reviewed-on: https://chromium-review.googlesource.com/c/1495527
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637103}
17 files changed