go.tools/playground/socket: add Native Client wrapper handling
go.tools/playground/socket: add Native Client wrapper handling

LGTM=adg
R=adg, dave, rsc, minux
CC=golang-codereviews
https://codereview.appspot.com/77240043

Committer: Andrew Gerrand <395a7d33bec8475c9b83b7d440f141bcbd994aa5@golang.org>

d0f/go-zh.tools,skyportsystems/go.tools,bryanxu/go-zh.tools,webfd/go-zh.tools,webfd/go-zh.tools,skyportsystems/go.tools,8limbs/gotools,skyportsystems/go.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,8limbs/gotools,webfd/go-zh.tools,webfd/go-zh.tools,d0f/go-zh.tools,d0f/go-zh.tools,bryanxu/go-zh.tools,8limbs/gotools,skyportsystems/go.tools,skyportsystems/go.tools,d0f/go-zh.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,d0f/go-zh.tools