diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/browser_477657.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/browser_477657.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,63 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+function test() {
+  /** Test for Bug 477657 **/
+  waitForExplicitFinish();
+
+  let newWin = openDialog(location, "_blank", "chrome,all,dialog=no");
+  newWin.addEventListener("load", function(aEvent) {
+    newWin.removeEventListener("load", arguments.callee, false);
+
+    let newState = { windows: [{
+      tabs: [{ entries: [] }],
+      _closedTabs: [{
+        state: { entries: [{ url: "about:" }]},
+        title: "About:"
+      }],
+      sizemode: "maximized"
+    }] };
+
+    let uniqueKey = "bug 477657";
+    let uniqueValue = "unik" + Date.now();
+
+    ss.setWindowValue(newWin, uniqueKey, uniqueValue);
+    is(ss.getWindowValue(newWin, uniqueKey), uniqueValue,
+       "window value was set before the window was overwritten");
+    ss.setWindowState(newWin, JSON.stringify(newState), true);
+
+    // use newWin.setTimeout(..., 0) to mirror sss_restoreWindowFeatures
+    newWin.setTimeout(function() {
+      is(ss.getWindowValue(newWin, uniqueKey), "",
+         "window value was implicitly cleared");
+
+      is(newWin.windowState, newWin.STATE_MAXIMIZED,
+         "the window was maximized");
+
+      is(JSON.parse(ss.getClosedTabData(newWin)).length, 1,
+         "the closed tab was added before the window was overwritten");
+      delete newState.windows[0]._closedTabs;
+      delete newState.windows[0].sizemode;
+      ss.setWindowState(newWin, JSON.stringify(newState), true);
+
+      newWin.setTimeout(function() {
+        is(JSON.parse(ss.getClosedTabData(newWin)).length, 0,
+           "closed tabs were implicitly cleared");
+
+        is(newWin.windowState, newWin.STATE_MAXIMIZED,
+           "the window remains maximized");
+        newState.windows[0].sizemode = "normal";
+        ss.setWindowState(newWin, JSON.stringify(newState), true);
+
+        newWin.setTimeout(function() {
+          isnot(newWin.windowState, newWin.STATE_MAXIMIZED,
+                "the window was explicitly unmaximized");
+
+          newWin.close();
+          finish();
+        }, 0);
+      }, 0);
+    }, 0);
+  }, false);
+}