Turn on GraphicsContext annotations when tracing.

In order to provide additional Picture debug info, trace-viewer needs GraphicsContext annotations. This CL enables annotations at the GC construction site when tracing cc.debug.

R=nduca@chromium.org,pdr@chromium.org
BUG=259433

Review URL: https://chromiumcodereview.appspot.com/18641010

git-svn-id: svn://svn.chromium.org/blink/trunk@154240 bbb929c8-8fbe-4397-9dbb-9b2b20218538