Auto generate MediaFeatureNames, its macros and MediaTypeNames

As part of the review of https://codereview.chromium.org/171383002/
it was requested that the required static strings for the media features and types will be generated as part of the build system.
This CL implements that request.

BUG=

Review URL: https://codereview.chromium.org/185533012

git-svn-id: svn://svn.chromium.org/blink/trunk@168465 bbb929c8-8fbe-4397-9dbb-9b2b20218538