Revert "Support warning decorations in Timeline flame chart based on trace events"
Revert "Build fix after r173654"

Reverts r173654 and r173655. Broke inspector/tracing-session-id.html.

TBR=yurys@chromium.org

Review URL: https://codereview.chromium.org/276793002

git-svn-id: svn://svn.chromium.org/blink/trunk@173701 bbb929c8-8fbe-4397-9dbb-9b2b20218538