Remove EventTarget interface from MediaDevices.idl
Remove EventTarget interface from MediaDevices.idl

We currently do not support events, and the IDL EventTarget declaration
was causing invalid casts in some tests, leading to security concerns.

BUG=501891

Review URL: https://codereview.chromium.org/1195633004

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@197488 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk,Pluto-tv/blink-crosswalk