ASSERTION FAILED: !node || node->isShadowRoot() in WebCore::EventRetargeter::eventTargetRespectingTargetRules
ASSERTION FAILED: !node || node->isShadowRoot() in WebCore::EventRetargeter::eventTargetRespectingTargetRules

Fix a potential bad cast in EventRetargeter::eventTargetRespectingTargetRules by explicitly checking
that the root node is shadow root before casting.

BUG=263386
TEST=None since testcase does not crash anymore on trunk and is not minimizable.

Review URL: https://chromiumcodereview.appspot.com/21926002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@155453 bbb929c8-8fbe-4397-9dbb-9b2b20218538

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