Add ExtensionPopup::OnWidgetActivationChanged checks.

Do not call the base BubbleDelegateView function impl.
(ExtensionPopup doesn't use its close_on_deactivate behavior)
Add checks for non-NULL widgets and !close_on_deactivate.

BUG=327776
TEST=Fewer crashes, better logging for remaining crashes.
R=sky@chromium.org

Review URL: https://codereview.chromium.org/101193006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241945 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241945