[SVG] Defer recursive detachAnimatedProperty call to avoid touching invalidated iterator.

This is a workaround patch for detachAnimatedProperty recursively being called for SVGSVGElement. This patch postpones the SVGAnimatedProperty dtor being called until we finish touching the HashMap, so it wont touch invalidated HashMap iterator.

BUG=333156

Review URL: https://codereview.chromium.org/133273005

git-svn-id: svn://svn.chromium.org/blink/trunk@165070 bbb929c8-8fbe-4397-9dbb-9b2b20218538