Do not use v8::CpuProfile::GetUid

This method is going to be deprecated in v8.

BUG=327298
R=alph@chromium.org

Review URL: https://codereview.chromium.org/117163003

git-svn-id: svn://svn.chromium.org/blink/trunk@164014 bbb929c8-8fbe-4397-9dbb-9b2b20218538