DevTools: Make WI.Target.Capabilities enum values uppercase

We've got all enum values starting with an uppercase letter in our code

TBR=sergeyv

Review URL: https://codereview.chromium.org/420783002

git-svn-id: svn://svn.chromium.org/blink/trunk@178924 bbb929c8-8fbe-4397-9dbb-9b2b20218538