Place the tracks code in the tracing namespace.

This updates all of the tracks exports to have a
namespace of tracing.tracks instead of just
tracks. This makes it more consistent wiht the
importer code.

Review URL: https://codereview.appspot.com/7397045

git-svn-id: https://trace-viewer.googlecode.com/svn/trunk@213 0e6d7f2b-9903-5b78-7403-59d27f066143
Sample importer + tests

Review URL: https://codereview.appspot.com/7371047

git-svn-id: https://trace-viewer.googlecode.com/svn/trunk@214 0e6d7f2b-9903-5b78-7403-59d27f066143