DevTools: Remove NativeMemory things from front-end

BUG=none
TEST=LayoutTests/*
R=yurys@chromium.org

Review URL: https://codereview.chromium.org/19569004

git-svn-id: svn://svn.chromium.org/blink/trunk@154399 bbb929c8-8fbe-4397-9dbb-9b2b20218538