Should updateDistributionIfNeeded before using ComposedTreeWalker in Node::normalize.

BUG=413207
TEST=fast/dom/shadow/normalize-progress-element-crash.html

Review URL: https://codereview.chromium.org/568733002

git-svn-id: svn://svn.chromium.org/blink/trunk@182038 bbb929c8-8fbe-4397-9dbb-9b2b20218538