Have Range constructor take a Document reference in argument

Have Range constructor take a Document reference in argument instead of
a pointer as the Document is expected to be non-null. Most callers
already have a reference so this avoids having to convert it into a
pointer.

Also update Range's ownerDocument() to return a reference as it can
never return NULL.

BUG=281400

Review URL: https://chromiumcodereview.appspot.com/23467007

git-svn-id: svn://svn.chromium.org/blink/trunk@157165 bbb929c8-8fbe-4397-9dbb-9b2b20218538