Have Node::ensureRareData() return a reference

Have Node::ensureRareData() return a reference instead of a pointer
as it can never return null. This makes the calling code look safer.

R=tkent
BUG=

Review URL: https://codereview.chromium.org/27519002

git-svn-id: svn://svn.chromium.org/blink/trunk@159864 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use Locale::queryString() instead of Platform::queryLocalizedString() for consistency.

BUG=298020
TEST=none; no behavior changes.

Review URL: https://codereview.chromium.org/27590004

git-svn-id: svn://svn.chromium.org/blink/trunk@159865 bbb929c8-8fbe-4397-9dbb-9b2b20218538