Timeline: do not rebuild presentation model when category filter changes

Since r168396, we were resetting and rebuilding TimelinePresentationModel
upon category filter change, which effectively lead to unability to see
any records under top-level records with hidden categories, since we were
resetting their expansion state to collapsed and filtering them out along
with all their children.

Drive-by: fix the bug with dispatching RecordAdded events from
TracingTimelineModel -- this should be done when removing complete event
from stack, not when we just added a fresh one.

BUG=
R=yurys@chromium.org

Review URL: https://codereview.chromium.org/349673002

git-svn-id: svn://svn.chromium.org/blink/trunk@176837 bbb929c8-8fbe-4397-9dbb-9b2b20218538