diff -r 000000000000 -r 6474c204b198 browser/devtools/debugger/test/browser_dbg_tracing-02.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/debugger/test/browser_dbg_tracing-02.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,78 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/**
+ * Test that we highlight matching calls and returns on hover.
+ */
+
+const TAB_URL = EXAMPLE_URL + "doc_tracing-01.html";
+
+let gTab, gDebuggee, gPanel, gDebugger;
+
+function test() {
+  SpecialPowers.pushPrefEnv({'set': [["devtools.debugger.tracer", true]]}, () => {
+    initDebugger(TAB_URL).then(([aTab, aDebuggee, aPanel]) => {
+      gTab = aTab;
+      gDebuggee = aDebuggee;
+      gPanel = aPanel;
+      gDebugger = gPanel.panelWin;
+
+      waitForSourceShown(gPanel, "code_tracing-01.js")
+        .then(() => startTracing(gPanel))
+        .then(clickButton)
+        .then(() => waitForClientEvents(aPanel, "traces"))
+        .then(highlightCall)
+        .then(testReturnHighlighted)
+        .then(unhighlightCall)
+        .then(testNoneHighlighted)
+        .then(() => stopTracing(gPanel))
+        .then(() => {
+          const deferred = promise.defer();
+          SpecialPowers.popPrefEnv(deferred.resolve);
+          return deferred.promise;
+        })
+        .then(() => closeDebuggerAndFinish(gPanel))
+        .then(null, aError => {
+          ok(false, "Got an error: " + aError.message + "\n" + aError.stack);
+        });
+    });
+  });
+}
+
+function clickButton() {
+  EventUtils.sendMouseEvent({ type: "click" },
+                            gDebuggee.document.querySelector("button"),
+                            gDebuggee);
+}
+
+function highlightCall() {
+  const callTrace = filterTraces(gPanel, t => t.querySelector(".trace-name[value=main]"))[0];
+  EventUtils.sendMouseEvent({ type: "mouseover" },
+                            callTrace,
+                            gDebugger);
+}
+
+function testReturnHighlighted() {
+  const returnTrace = filterTraces(gPanel, t => t.querySelector(".trace-name[value=main]"))[1];
+  ok(Array.indexOf(returnTrace.querySelector(".trace-item").classList, "selected-matching") >= 0,
+     "The corresponding return log should be highlighted.");
+}
+
+function unhighlightCall() {
+  const callTrace = filterTraces(gPanel, t => t.querySelector(".trace-name[value=main]"))[0];
+  EventUtils.sendMouseEvent({ type: "mouseout" },
+                            callTrace,
+                            gDebugger);
+}
+
+function testNoneHighlighted() {
+  const highlightedTraces = filterTraces(gPanel, t => t.querySelector(".selected-matching"));
+  is(highlightedTraces.length, 0, "Shouldn't have any highlighted traces");
+}
+
+registerCleanupFunction(function() {
+  gTab = null;
+  gDebuggee = null;
+  gPanel = null;
+  gDebugger = null;
+});