Update README now that we don't need anything outside GardeningServer

Now that we don't use qunit, the http server can be started from
within the GardeningServer directory.

TBR=michaelpg@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/489733002

git-svn-id: svn://svn.chromium.org/blink/trunk@180631 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Support invalidation sets for negated selectors.

Add invalidation set features to invalidation sets for negated classes, ids,
etc. But still treat negated features as universal selectors and trigger
subtree recalc.

Example selector -> invalidation set mappings:

":not(.a)"    -> ".a {}"
":not(.a) .b" -> ".b {}, .a { .b }"
".a :not(.b)"  -> ".a { * }, .b {}"
".a .b:not(.c)" -> ".a { .b }, .b {}, .c {}"

BUG=377939

Review URL: https://codereview.chromium.org/462593002

git-svn-id: svn://svn.chromium.org/blink/trunk@180632 bbb929c8-8fbe-4397-9dbb-9b2b20218538