Remove WrapperTypeTraits

WrapperTypeTraits is unnecessary.
This CL replaces WrapperTypeTraits<X>::wrapperTypeInfo() with &V8X::wrapperTypeInfo,
and removes WrapperTypeTraits completely.

NOTRY=true

Review URL: https://codereview.chromium.org/172033002

git-svn-id: svn://svn.chromium.org/blink/trunk@167409 bbb929c8-8fbe-4397-9dbb-9b2b20218538