Close embedded extension options page when the overlay is hidden
Previously, when the embedded extension options page was hidden through
an unexpected event (i.e. not via Esc or via the Close button, but via
a script, e.g. by bug 445918), the extension options page would not be
removed even though it was hidden.
This patch fixes the problem by triggering the page destruction handlers
(ExtensionOptionsOverlay.prototype.handleDismiss_) via the cancelOverlay
event.
BUG=445978
R=finnur@chromium.org
Review URL: https://codereview.chromium.org/
831063002
Cr-Commit-Position: refs/heads/master@{#310763}