message: Add explain comment for synthetic trace path
diff: @@ -392,9 +392,10 @@ Raven.prototype = {
  if (this._globalOptions.stacktrace || (options && options.stacktrace)) {
  var ex;
  - // create a stack trace from this point; just trim
  - // off extra frames so they don't include this function call (or
  - // earlier Raven.js library fn calls)
  + // Generate a "synthetic" stack trace from this point.
  + // NOTE: If you are a Sentry user, and you are seeing this stack frame, it is NOT indicative
  + // of a bug with Raven.js. Sentry generates synthetic traces either by configuration,
  + // or if it catches a thrown object without a "stack" property.
  try {
  throw new Error(msg);
  } catch (ex1) {
  @@ -408,6 +409,9 @@ Raven.prototype = {
  // fingerprint on msg, not stack trace (legacy behavior, could be
  // revisited)
  fingerprint: msg,
  + // since we know this is a synthetic trace, the top N-most frames
  + // MUST be from Raven.js, so mark them as in_app later by setting
  + // trimHeadFrames
  trimHeadFrames: (options.trimHeadFrames || 0) + 1
  }, options);
  