Improve filtering for false positive crashes

...by inspecting if the module with the crash has the topmost handler
in the SEH chain.  If that's the case then the exception will very
likely be handled. This covers the case of IsBadReadPtr adn family
without any special code. It also lets us address IsValidInterface,
an internal helper in urlmon.

BUG=64348
TEST=covered by existing unit tests

Review URL: http://codereview.chromium.org/5622006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@69066 0039d316-1c4b-4281-b951-d872f2087c98