w3c deps roll for layout tests: import IndexedDB, mediacapture-streams

This is patch 1 of 4.

TBR=phoglund@chromium.org, jsbell@chromium.org, cmumford@chromium.org
BUG=404303, 404305

Review URL: https://codereview.chromium.org/478863002

git-svn-id: svn://svn.chromium.org/blink/trunk@180416 bbb929c8-8fbe-4397-9dbb-9b2b20218538