DevTools: Remove event filtering from tracing timeline event flamechart

We cannot do filtering at this point, as the flamechart items are built
basing on the recorded trace event levels. Thus if an event is filtered
out its children will hang in the air.

R=loislo@chromium.org

Review URL: https://codereview.chromium.org/370783002

git-svn-id: svn://svn.chromium.org/blink/trunk@177544 bbb929c8-8fbe-4397-9dbb-9b2b20218538