Bug 1313326 - Part 3: Update about:telemetry to show child process events. r=dexter

toolkit/content/aboutTelemetry.js

@@ -314,6 +314,8 @@ var PingPicker = {
             .addEventListener("change", () => displayPingData(gPingData));
     document.getElementById("keyed-histograms-processes")
             .addEventListener("change", () => displayPingData(gPingData));
+    document.getElementById("events-processes")
+            .addEventListener("change", () => displayPingData(gPingData));
   },
 
   onPingSourceChanged() {
@@ -1734,7 +1736,16 @@ var Events = {
       return;
     }
 
-    const events = aPayload.processes.parent.events;
+    let processesSelect = document.getElementById("events-processes");
+    let selectedProcess = processesSelect.selectedOptions.item(0).getAttribute("value");
+
+    if (!aPayload.processes ||
+        !selectedProcess ||
+        !(selectedProcess in aPayload.processes)) {
+      return;
+    }
+
+    let events = aPayload.processes[selectedProcess].events;
     const hasData = events && Object.keys(events).length > 0;
     setHasData("events-section", hasData);
     if (!hasData) {
@@ -2082,6 +2093,7 @@ function displayPingData(ping, updatePayloadList = false) {
     renderProcessList(ping, document.getElementById("keyed-scalars-processes"));
     renderProcessList(ping, document.getElementById("histograms-processes"));
     renderProcessList(ping, document.getElementById("keyed-histograms-processes"));
+    renderProcessList(ping, document.getElementById("events-processes"));
   }
 
   // Show general data.

toolkit/content/aboutTelemetry.xhtml

@@ -191,6 +191,9 @@
         <h1 class="section-name">&aboutTelemetry.eventsSection;</h1>
         <span class="toggle-caption">&aboutTelemetry.toggle;</span>
         <span class="empty-caption">&aboutTelemetry.emptySection;</span>
+        <div class="processes-ui">
+          <select id="events-processes" class="process-picker"></select>
+        </div>
         <div id="events" class="data">
         </div>
       </section>