code: function (classpath, msg) {
              this._logs[this._nbLogs++] = {
                  classpath : classpath,
                  msg : msg,
                  id : this._ids,
                  start : (new Date()).getTime()
              };
              return this._ids++;
          }
docs: Starts a time measure. Returns the id used to stop the measure.
  @param {String} classpath
  @param {String} msg
  @return {Number} profilingId