Added the ability to associate trace information with failing specs

This is meant to aid in debugging failures, particularly intermittent
failures, in cases where interactive debugging or console.log aren't
suitable.

src/core/Spec.js

@@ -68,8 +68,9 @@ getJasmineRequireObj().Spec = function(j$) {
      * @property {String} status - Once the spec has completed, this string represents the pass/fail status of this spec.
      * @property {number} duration - The time in ms used by the spec execution, including any before/afterEach.
      * @property {Object} properties - User-supplied properties, if any, that were set using {@link Env#setSpecProperty}
+     * @property {TraceEntry[]|null} trace - Trace messages, if any, that were logged using {@link Env#trace} during a failing spec.
      * @since 2.0.0
-x     */
+     */
     this.result = {
       id: this.id,
       description: this.description,
@@ -79,7 +80,8 @@ x     */
       deprecationWarnings: [],
       pendingReason: '',
       duration: null,
-      properties: null
+      properties: null,
+      trace: null
     };
   }
 
@@ -124,6 +126,11 @@ x     */
         self.queueableFn.fn = null;
         self.result.status = self.status(excluded, failSpecWithNoExp);
         self.result.duration = self.timer.elapsed();
+
+        if (self.result.status !== 'failed') {
+          self.result.trace = null;
+        }
+
         self.resultCallback(self.result, done);
       }
     };
@@ -235,6 +242,20 @@ x     */
     );
   };
 
+  Spec.prototype.trace = function(msg) {
+    if (!this.result.trace) {
+      this.result.trace = [];
+    }
+
+    /**
+     * @typedef TraceEntry
+     * @property {String} message - The message that was passed to {@link Env#trace}.
+     * @property {number} timestamp - The time when the entry was added, in
+     * milliseconds from the spec's start time
+     */
+    this.result.trace.push({ message: msg, timestamp: this.timer.elapsed() });
+  };
+
   var extractCustomPendingMessage = function(e) {
     var fullMessage = e.toString(),
       boilerplateStart = fullMessage.indexOf(Spec.pendingSpecExceptionMessage),