diff -r 000000000000 -r 6474c204b198 browser/components/sessionstore/test/browser_scrollPositions.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/sessionstore/test/browser_scrollPositions.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,136 @@
+/* Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+const URL = ROOT + "browser_scrollPositions_sample.html";
+const URL_FRAMESET = ROOT + "browser_scrollPositions_sample_frameset.html";
+
+// Randomized set of scroll positions we will use in this test.
+const SCROLL_X = Math.round(100 * (1 + Math.random()));
+const SCROLL_Y = Math.round(200 * (1 + Math.random()));
+const SCROLL_STR = SCROLL_X + "," + SCROLL_Y;
+
+const SCROLL2_X = Math.round(300 * (1 + Math.random()));
+const SCROLL2_Y = Math.round(400 * (1 + Math.random()));
+const SCROLL2_STR = SCROLL2_X + "," + SCROLL2_Y;
+
+/**
+ * This test ensures that we properly serialize and restore scroll positions
+ * for an average page without any frames.
+ */
+add_task(function test_scroll() {
+  let tab = gBrowser.addTab(URL);
+  let browser = tab.linkedBrowser;
+  yield promiseBrowserLoaded(browser);
+
+  // Scroll down a little.
+  yield sendMessage(browser, "ss-test:setScrollPosition", {x: SCROLL_X, y: SCROLL_Y});
+  checkScroll(tab, {scroll: SCROLL_STR}, "scroll is fine");
+
+  // Duplicate and check that the scroll position is restored.
+  let tab2 = ss.duplicateTab(window, tab);
+  let browser2 = tab2.linkedBrowser;
+  yield promiseTabRestored(tab2);
+
+  let scroll = yield sendMessage(browser2, "ss-test:getScrollPosition");
+  is(JSON.stringify(scroll), JSON.stringify({x: SCROLL_X, y: SCROLL_Y}),
+    "scroll position has been duplicated correctly");
+
+  // Check that reloading retains the scroll positions.
+  browser2.reload();
+  yield promiseBrowserLoaded(browser2);
+  checkScroll(tab2, {scroll: SCROLL_STR}, "reloading retains scroll positions");
+
+  // Check that a force-reload resets scroll positions.
+  browser2.reloadWithFlags(Ci.nsIWebNavigation.LOAD_FLAGS_BYPASS_CACHE);
+  yield promiseBrowserLoaded(browser2);
+  checkScroll(tab2, null, "force-reload resets scroll positions");
+
+  // Scroll back to the top and check that the position has been reset. We
+  // expect the scroll position to be "null" here because there is no data to
+  // be stored if the frame is in its default scroll position.
+  yield sendMessage(browser, "ss-test:setScrollPosition", {x: 0, y: 0});
+  checkScroll(tab, null, "no scroll stored");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+  gBrowser.removeTab(tab2);
+});
+
+/**
+ * This tests ensures that we properly serialize and restore scroll positions
+ * for multiple frames of pages with framesets.
+ */
+add_task(function test_scroll_nested() {
+  let tab = gBrowser.addTab(URL_FRAMESET);
+  let browser = tab.linkedBrowser;
+  yield promiseBrowserLoaded(browser);
+
+  // Scroll the first child frame down a little.
+  yield sendMessage(browser, "ss-test:setScrollPosition", {x: SCROLL_X, y: SCROLL_Y, frame: 0});
+  checkScroll(tab, {children: [{scroll: SCROLL_STR}]}, "scroll is fine");
+
+  // Scroll the second child frame down a little.
+  yield sendMessage(browser, "ss-test:setScrollPosition", {x: SCROLL2_X, y: SCROLL2_Y, frame: 1});
+  checkScroll(tab, {children: [{scroll: SCROLL_STR}, {scroll: SCROLL2_STR}]}, "scroll is fine");
+
+  // Duplicate and check that the scroll position is restored.
+  let tab2 = ss.duplicateTab(window, tab);
+  let browser2 = tab2.linkedBrowser;
+  yield promiseTabRestored(tab2);
+
+  let scroll = yield sendMessage(browser2, "ss-test:getScrollPosition", {frame: 0});
+  is(JSON.stringify(scroll), JSON.stringify({x: SCROLL_X, y: SCROLL_Y}),
+    "scroll position #1 has been duplicated correctly");
+
+  scroll = yield sendMessage(browser2, "ss-test:getScrollPosition", {frame: 1});
+  is(JSON.stringify(scroll), JSON.stringify({x: SCROLL2_X, y: SCROLL2_Y}),
+    "scroll position #2 has been duplicated correctly");
+
+  // Check that resetting one frame's scroll position removes it from the
+  // serialized value.
+  yield sendMessage(browser, "ss-test:setScrollPosition", {x: 0, y: 0, frame: 0});
+  checkScroll(tab, {children: [null, {scroll: SCROLL2_STR}]}, "scroll is fine");
+
+  // Check the resetting all frames' scroll positions nulls the stored value.
+  yield sendMessage(browser, "ss-test:setScrollPosition", {x: 0, y: 0, frame: 1});
+  checkScroll(tab, null, "no scroll stored");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+  gBrowser.removeTab(tab2);
+});
+
+/**
+ * This test ensures that by moving scroll positions out of tabData.entries[]
+ * we still support the old scroll data format stored per shistory entry.
+ */
+add_task(function test_scroll_old_format() {
+  const TAB_STATE = { entries: [{url: URL, scroll: SCROLL_STR}] };
+
+  // Add a blank tab.
+  let tab = gBrowser.addTab("about:blank");
+  let browser = tab.linkedBrowser;
+  yield promiseBrowserLoaded(browser);
+
+  // Apply the tab state with the old format.
+  ss.setTabState(tab, JSON.stringify(TAB_STATE));
+  yield promiseTabRestored(tab);
+
+  // Check that the scroll positions has been applied.
+  let scroll = yield sendMessage(browser, "ss-test:getScrollPosition");
+  is(JSON.stringify(scroll), JSON.stringify({x: SCROLL_X, y: SCROLL_Y}),
+    "scroll position has been restored correctly");
+
+  // Cleanup.
+  gBrowser.removeTab(tab);
+});
+
+function checkScroll(tab, expected, msg) {
+  let browser = tab.linkedBrowser;
+  SyncHandlers.get(browser).flush();
+
+  let scroll = JSON.parse(ss.getTabState(tab)).scroll || null;
+  is(JSON.stringify(scroll), JSON.stringify(expected), msg);
+}