DevTools: drive-by fixes for OverridesSupport
DevTools: drive-by fixes for OverridesSupport

All of a sudden, all usages of XOR operator in OverridesSupport
turned out to be erroneous. The patch fixes this.

R=pfeldman

Review URL: https://codereview.chromium.org/805413007

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@187542 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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