Shape-Inside Should Not Be Shared To Descendants of Inline or Floating Elements

The test for sharing ShapeInsideInfo sharing was insufficient to catch
shadow children of elements (such as text controls).

BUG=317819

Review URL: https://codereview.chromium.org/109023002

git-svn-id: svn://svn.chromium.org/blink/trunk@164120 bbb929c8-8fbe-4397-9dbb-9b2b20218538