runtime: fix bug in cpu profiler Number of lost samples was overcounted (never reset). Also remove unused variable (it's trivial to restore it for debugging if needed).
runtime: fix bug in cpu profiler
Number of lost samples was overcounted (never reset).
Also remove unused variable (it's trivial to restore it for debugging if needed).

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews, rsc
https://codereview.appspot.com/96060043

d0f/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,d0f/go-zh,bryanxu/go-zh,webfd/go-zh,bryanxu/go-zh,bryanxu/go-zh,d0f/go-zh,d0f/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,webfd/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,bryanxu/go-zh,sanjosh/sanjos100-tipc,bryanxu/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,d0f/go-zh,webfd/go-zh,webfd/go-zh,bryanxu/go-zh,d0f/go-zh,webfd/go-zh,webfd/go-zh