go.tools/dashboard/app: update CL threads with perf notifications
go.tools/dashboard/app: update CL threads with perf notifications

LGTM=dvyukov
R=dvyukov
CC=golang-codereviews, rsc
https://codereview.appspot.com/135460043

d0f/go-zh.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,bryanxu/go-zh.tools,d0f/go-zh.tools,bryanxu/go-zh.tools,d0f/go-zh.tools,d0f/go-zh.tools,webfd/go-zh.tools,webfd/go-zh.tools,webfd/go-zh.tools,bryanxu/go-zh.tools,webfd/go-zh.tools,d0f/go-zh.tools