Tracing: make filtering logic more intuitive for multiple categories

This changes the way category filter processes multi-categories groups.
Previously, adding a disabled-by-default- category to a regular category
would prevent the event from matching filter if only regular category
is enabled. This is somewhat counter-intuitive, the expected behavior
is that each category is processed by the filter independently. The new
logic is:

1. if at least one category in event category group matches at
least one category enabled in the filter, the event passes;

2. if at least one category in event category group matches at least
one category explicitly excluded in the filter, the event is
filtered out;

3. the event is passed by default, if included categories list is empty
and event has at least one category that is not disabled-by-default-.

Note no existing tests were modified (though I'm not sure if (2) should
be the way it is).

BUG=

Review URL: https://codereview.chromium.org/788243003

Cr-Commit-Position: refs/heads/master@{#308136}

0 files changed, 0 insertions, 0 deletions