1 files changed, 58 insertions, 0 deletions
diff --git a/browser/components/sessionstore/test/browser_687710.js b/browser/components/sessionstore/test/browser_687710.js
new file mode 100644
index 0000000000..e90c74c881
--- /dev/null
+++ b/browser/components/sessionstore/test/browser_687710.js
@@ -0,0 +1,58 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Test that sessionrestore handles cycles in the shentry graph properly.
+//
+// These cycles shouldn't be there in the first place, but they cause hangs
+// when they mysteriously appear (bug 687710).  Docshell code assumes this
+// graph is a tree and tires to walk to the root.  But if there's a cycle,
+// there is no root, and we loop forever.
+
+var stateBackup = ss.getBrowserState();
+
+var state = {
+  windows: [
+    {
+      tabs: [
+        {
+          entries: [
+            {
+              docIdentifier: 1,
+              url: "http://example.com",
+              triggeringPrincipal_base64,
+              children: [
+                {
+                  docIdentifier: 2,
+                  url: "http://example.com",
+                  triggeringPrincipal_base64,
+                },
+              ],
+            },
+            {
+              docIdentifier: 2,
+              url: "http://example.com",
+              triggeringPrincipal_base64,
+              children: [
+                {
+                  docIdentifier: 1,
+                  url: "http://example.com",
+                  triggeringPrincipal_base64,
+                },
+              ],
+            },
+          ],
+        },
+      ],
+    },
+  ],
+};
+
+add_task(async function test() {
+  registerCleanupFunction(function () {
+    ss.setBrowserState(stateBackup);
+  });
+
+  /* This test fails by hanging. */
+  await setBrowserState(state);
+  ok(true, "Didn't hang!");
+});