Update gypi in extensions after move and removal of headers.

Fixes warnings in the gyp msvs-ninja generator.

Followup to
https://codereview.chromium.org/892923002 (guest_view_messages.h)
https://codereview.chromium.org/913393003 (extension_view.js)
https://codereview.chromium.org/820513002 (surface_worker.js,
    and surface_view.js)
https://codereview.chromium.org/654043002 (web_view.js,
    web_view_events.js and web_view_experimental.js)

R=fsamuel@chromium.org,kalman@chromium.org,apacible@chromium.org,rockot@chromium.org
BUG=459058,444869,459680,434226

Review URL: https://codereview.chromium.org/952513002

Cr-Commit-Position: refs/heads/master@{#317767}
1 file changed