diff -r 000000000000 -r 6474c204b198 browser/devtools/webconsole/test/browser_webconsole_bug_613642_prune_scroll.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/webconsole/test/browser_webconsole_bug_613642_prune_scroll.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,97 @@
+/* vim:set ts=2 sw=2 sts=2 et: */
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/
+ *
+ * Contributor(s):
+ *   Mihai Șucan <mihai.sucan@gmail.com>
+ */
+
+let hud, testDriver;
+
+function testNext() {
+  testDriver.next();
+}
+
+function testGen() {
+  hud.jsterm.clearOutput();
+
+  let outputNode = hud.outputNode;
+
+  Services.prefs.setIntPref("devtools.hud.loglimit.console", 140);
+  let scrollBoxElement = outputNode.parentNode;
+
+  for (let i = 0; i < 150; i++) {
+    content.console.log("test message " + i);
+  }
+
+  waitForMessages({
+    webconsole: hud,
+    messages: [{
+      text: "test message 149",
+      category: CATEGORY_WEBDEV,
+      severity: SEVERITY_LOG,
+    }],
+  }).then(testNext);
+
+  yield undefined;
+
+  let oldScrollTop = scrollBoxElement.scrollTop;
+  isnot(oldScrollTop, 0, "scroll location is not at the top");
+
+  let firstNode = outputNode.firstChild;
+  ok(firstNode, "found the first message");
+
+  let msgNode = outputNode.children[80];
+  ok(msgNode, "found the 80th message");
+
+  // scroll to the middle message node
+  msgNode.scrollIntoView(false);
+
+  isnot(scrollBoxElement.scrollTop, oldScrollTop,
+        "scroll location updated (scrolled to message)");
+
+  oldScrollTop = scrollBoxElement.scrollTop;
+
+  // add a message
+  content.console.log("hello world");
+
+  waitForMessages({
+    webconsole: hud,
+    messages: [{
+      text: "hello world",
+      category: CATEGORY_WEBDEV,
+      severity: SEVERITY_LOG,
+    }],
+  }).then(testNext);
+
+  yield undefined;
+
+  // Scroll location needs to change, because one message is also removed, and
+  // we need to scroll a bit towards the top, to keep the current view in sync.
+  isnot(scrollBoxElement.scrollTop, oldScrollTop,
+        "scroll location updated (added a message)");
+
+  isnot(outputNode.firstChild, firstNode,
+        "first message removed");
+
+  Services.prefs.clearUserPref("devtools.hud.loglimit.console");
+
+  hud = testDriver = null;
+  finishTest();
+
+  yield undefined;
+}
+
+function test() {
+  addTab("data:text/html;charset=utf-8,Web Console test for bug 613642: maintain scroll with pruning of old messages");
+  browser.addEventListener("load", function tabLoad(aEvent) {
+    browser.removeEventListener(aEvent.type, tabLoad, true);
+
+    openConsole(null, function(aHud) {
+      hud = aHud;
+      testDriver = testGen();
+      testDriver.next();
+    });
+  }, true);
+}