Always initialize all members of WebWindowFeatures.
Always initialize all members of WebWindowFeatures.

Prevents information leaks across the wire.

BUG=chromium:393981
R=jochen@chromium.org

Review URL: https://codereview.chromium.org/392973002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@178199 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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