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diff --git a/dom/browser-element/mochitest/priority/test_WebGLContextLost.html b/dom/browser-element/mochitest/priority/test_WebGLContextLost.html
new file mode 100644
index 000000000..383506ec6
--- /dev/null
+++ b/dom/browser-element/mochitest/priority/test_WebGLContextLost.html
@@ -0,0 +1,99 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+Test that calling setVisible('false') and then sending a low-memory
+notification causes a WebGL context loss event.
+-->
+<head>
+  <script type="application/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="application/javascript" src="../browserElementTestHelpers.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
+</head>
+<body>
+
+<script type="application/javascript;version=1.7">
+"use strict";
+
+SimpleTest.waitForExplicitFinish();
+browserElementTestHelpers.setEnabledPref(true);
+browserElementTestHelpers.addPermission();
+browserElementTestHelpers.enableProcessPriorityManager();
+
+function runTest() {
+  var iframe = document.createElement('iframe');
+  iframe.setAttribute('mozbrowser', true);
+  iframe.src = 'file_WebGLContextLost.html';
+
+  // We use this to ensure that we don't call SimpleTest.finish() twice.
+  var finished = false;
+  function finishOnce() {
+    if (!finished) {
+      SimpleTest.finish();
+      finished = true;
+    }
+  }
+
+  expectMozbrowserEvent(iframe, 'error').then(function(e) {
+    if (finished) {
+      // We don't care if the frame dies after the test finishes.
+      return;
+    }
+    todo(false, "child process is crashing; this probably indicates that " +
+         "something is wrong with WebGL in child processes on your machine.");
+    is(e.detail.type, 'fatal');
+  }).then(finishOnce);
+
+  var childID = null;
+  Promise.all([
+    expectOnlyOneProcessCreated('FOREGROUND').then(function(chid) {
+      childID = chid;
+    }),
+    expectMozbrowserEvent(iframe, 'loadend'),
+    expectMozbrowserEvent(iframe, 'showmodalprompt').then(function(e) {
+      is(e.detail.message, 'ready');
+    })
+  ]).then(function() {
+    // Fire a low-memory notification once the process goes into the background
+    // due to the setVisible(false) call below.
+    expectPriorityChange(childID, 'BACKGROUND').then(function() {
+      SimpleTest.executeSoon(function() {
+        var os = SpecialPowers.Cc["@mozilla.org/observer-service;1"]
+                              .getService(SpecialPowers.Ci.nsIObserverService);
+        os.notifyObservers(null, "memory-pressure", "low-memory");
+        ok(true, 'Successfully notified observers.');
+      });
+    });
+
+    // This test isn't the only possible source of a low-memory notification; the
+    // browser can fire one whenever it likes.  So it's fine if we lose the
+    // WebGL context before we fire the low-memory notification ourself.
+
+    var p = expectMozbrowserEvent(iframe, 'showmodalprompt').then(function(e) {
+      is(e.detail.message, 'webglcontextlost');
+    });
+
+    iframe.setVisible(false);
+    return p;
+  }).then(finishOnce);
+
+  document.body.appendChild(iframe);
+}
+
+addEventListener('testready', function() {
+  // At the time this test was written, webgl was blocklisted inside child
+  // processes on desktop Linux.  The issue is that we spawn a child process to
+  // read driver info, but we only did this on the main prrocess.  Child
+  // processes never read the driver info themselves, nor do they get it from
+  // their parent, so they refuse to start up WebGL.
+  //
+  // This isn't a problem on B2G because we force WebGL on there.  But it
+  // obviously makes this test difficult.  bjacob says forcing WebGL on here
+  // shouldn't hurt things, and anyway this setting mirrors what we do on B2G,
+  // which is what we're trying to test!
+  SpecialPowers.pushPrefEnv({set: [["webgl.force-enabled", true]]},
+                            runTest);
+});
+
+</script>
+</body>
+</html>