[Tracing] Create TracingCategoryObserver in gin/.

Previously we implemented TracingCategoryObserver in V8 in order to do fast
category check when we enable V8 specific tracing feature in a unified way.
This patch calls the the creation of TracingCategoryObserver from chrome and
adds it to observer list.

BUG=v8:5590

Review-Url: https://codereview.chromium.org/2456073004
Cr-Commit-Position: refs/heads/master@{#428756}
1 file changed