Revert "Remove MediaKeys.isTypeSupported()."

This reverts commit f3bca1bfe191b94af316a54bb55dec53ec4f4cf2.

Reasons for revert:

Various encrypt-media tests have started to fail (flakily on some bots),

 http://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=media%2Fencrypted-media%2Fencrypted-media-lifetime-mediakeys-with-session.html%2Cmedia%2Fencrypted-media%2Fencrypted-media-lifetime-mediakeysession-reference.html%2Cmedia%2Fencrypted-media%2Fencrypted-media-lifetime-mediakeysession-release-noreference.html%2Cmedia%2Fencrypted-media%2Fencrypted-media-lifetime-mediakeysession-release.html%2Cmedia%2Fencrypted-media%2Fencrypted-media-lifetime-multiple-mediakeys.html

TBR=jrummell,ddorwin
BUG=425186
NOTRY=true

Review URL: https://codereview.chromium.org/806653004

git-svn-id: svn://svn.chromium.org/blink/trunk@187122 bbb929c8-8fbe-4397-9dbb-9b2b20218538
6 files changed
tree: f9e35344de22c4ec2bd435c321232b7aff726783
  1. third_party/