DevTools: Implement "close tabs to the right" for Sources panel tabs
DevTools: Implement "close tabs to the right" for Sources panel tabs

The patch implements "close tabs to the right" functionality for the
sources panel tabs.

BUG=424298
R=vsevik

Review URL: https://codereview.chromium.org/849073006

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@188628 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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