Bug 1399605 - [intersection-observer] Check if target is actually being observed when unobserving. r=mrbkap

--HG-- extra : rebase_source : d3c8c012dba2941b230cdfbf332ab3c77b7a26ef
2017-09-19 10:50:10 -07:00 · 2017-09-19 10:50:10 -07:00 · 2b102d3c56
--- a/dom/base/DOMIntersectionObserver.cpp
+++ b/dom/base/DOMIntersectionObserver.cpp
@ -161,6 +161,10 @@ DOMIntersectionObserver::Observe(Element& aTarget)
 void
 DOMIntersectionObserver::Unobserve(Element& aTarget)
 {
+  if (!mObservationTargets.Contains(&aTarget)) {
+    return;
+  }
+
  if (mObservationTargets.Length() == 1) {
    Disconnect();
    return;
--- a/dom/base/test/mochitest.ini
+++ b/dom/base/test/mochitest.ini
@ -623,6 +623,7 @@ skip-if = toolkit == 'android'
 [test_bug1375050.html]
 [test_bug1381710.html]
 [test_bug1384658.html]
+[test_bug1399605.html]
 skip-if = toolkit == 'android'
 [test_caretPositionFromPoint.html]
 [test_change_policy.html]
--- a/dom/base/test/test_bug1399605.html
+++ b/dom/base/test/test_bug1399605.html
@ -0,0 +1,31 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Test for Bug 1399605</title>
+  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1399605">Mozilla Bug 1399605</a>
+<p id="display"></p>
+<div id="content">
+  <div id="target"></div>
+</div>
+<pre id="test">
+<script type="application/javascript">
+
+  let observer = new IntersectionObserver(function() {
+    ok(true, "we are still observing");
+    SimpleTest.finish();
+  });
+  observer.observe(document.getElementById('target'));
+  observer.unobserve(document.getElementById('content'));
+  SimpleTest.waitForExplicitFinish();
+
+</script>
+</pre>
+<div id="log">
+</div>
+</body>
+</html>