Bug 1034138 - c. Display thread hang native stack in about:telemetry if available; r=vladan

toolkit/content/aboutTelemetry.js

@@ -443,7 +443,8 @@ let ThreadHangStats = {
       let hangDiv = Histogram.render(
         div, hangName, hang.histogram, {exponential: true});
       let stackDiv = document.createElement("div");
-      hang.stack.forEach((frame) => {
+      let stack = hang.nativeStack || hang.stack;
+      stack.forEach((frame) => {
         stackDiv.appendChild(document.createTextNode(frame));
         // Leave an extra <br> at the end of the stack listing
         stackDiv.appendChild(document.createElement("br"));