diff --git a/browser/base/content/tab-content.js b/browser/base/content/tab-content.js
index c4e51951116a..bddc5c5a5718 100644
--- a/browser/base/content/tab-content.js
+++ b/browser/base/content/tab-content.js
@@ -64,6 +64,7 @@ addMessageListener("Browser:HideSessionRestoreButton", function(message) {
 });
 
 
+// XXX(nika): Should we try to call this in the parent process instead?
 addMessageListener("Browser:Reload", function(message) {
   /* First, we'll try to use the session history object to reload so
    * that framesets are handled properly. If we're in a special
@@ -73,9 +74,9 @@ addMessageListener("Browser:Reload", function(message) {
 
   let webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
   try {
-    let sh = webNav.sessionHistory;
-    if (sh)
-      webNav = sh.QueryInterface(Ci.nsIWebNavigation);
+    if (webNav.sessionHistory) {
+      webNav = webNav.sessionHistory;
+    }
   } catch (e) {
   }
 
diff --git a/browser/base/content/test/general/browser_e10s_switchbrowser.js b/browser/base/content/test/general/browser_e10s_switchbrowser.js
index b119a92774e5..61380ae4044c 100644
--- a/browser/base/content/test/general/browser_e10s_switchbrowser.js
+++ b/browser/base/content/test/general/browser_e10s_switchbrowser.js
@@ -19,7 +19,7 @@ function get_remote_history(browser) {
     };
 
     for (let i = 0; i < sessionHistory.count; i++) {
-      let entry = sessionHistory.getEntryAtIndex(i, false);
+      let entry = sessionHistory.legacySHistory.getEntryAtIndex(i, false);
       result.entries.push({
         uri: entry.URI.spec,
         title: entry.title
diff --git a/browser/base/content/web-panels.js b/browser/base/content/web-panels.js
index 96a42cc02743..04d6d6dbad66 100644
--- a/browser/base/content/web-panels.js
+++ b/browser/base/content/web-panels.js
@@ -93,6 +93,5 @@ function PanelBrowserStop() {
 function PanelBrowserReload() {
     getPanelBrowser().webNavigation
                      .sessionHistory
-                     .QueryInterface(Ci.nsIWebNavigation)
                      .reload(Ci.nsIWebNavigation.LOAD_FLAGS_NONE);
 }
diff --git a/browser/components/sessionstore/ContentRestore.jsm b/browser/components/sessionstore/ContentRestore.jsm
index 5e11aa9a14bc..cbb0eb2f92dd 100644
--- a/browser/components/sessionstore/ContentRestore.jsm
+++ b/browser/components/sessionstore/ContentRestore.jsm
@@ -164,7 +164,7 @@ ContentRestoreInternal.prototype = {
       this.restoreTabContent(null, false, callbacks.onLoadFinished);
     });
 
-    webNavigation.sessionHistory.addSHistoryListener(listener);
+    webNavigation.sessionHistory.legacySHistory.addSHistoryListener(listener);
     this._historyListener = listener;
 
     // Make sure to reset the capabilities and attributes in case this tab gets
@@ -203,7 +203,7 @@ ContentRestoreInternal.prototype = {
     this._tabData = null;
 
     let webNavigation = this.docShell.QueryInterface(Ci.nsIWebNavigation);
-    let history = webNavigation.sessionHistory;
+    let history = webNavigation.sessionHistory.legacySHistory;
 
     // Listen for the tab to finish loading.
     this.restoreTabContentStarted(finishCallback);
@@ -365,7 +365,7 @@ ContentRestoreInternal.prototype = {
  */
 function HistoryListener(docShell, callback) {
   let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
-  webNavigation.sessionHistory.addSHistoryListener(this);
+  webNavigation.sessionHistory.legacySHistory.addSHistoryListener(this);
 
   this.webNavigation = webNavigation;
   this.callback = callback;
@@ -377,7 +377,7 @@ HistoryListener.prototype = {
   ]),
 
   uninstall() {
-    let shistory = this.webNavigation.sessionHistory;
+    let shistory = this.webNavigation.sessionHistory.legacySHistory;
     if (shistory) {
       shistory.removeSHistoryListener(this);
     }
diff --git a/browser/components/sessionstore/content/content-sessionStore.js b/browser/components/sessionstore/content/content-sessionStore.js
index 7a93061717fd..023f94e6b24f 100644
--- a/browser/components/sessionstore/content/content-sessionStore.js
+++ b/browser/components/sessionstore/content/content-sessionStore.js
@@ -320,8 +320,8 @@ var SessionHistoryListener = {
     // waiting to add the listener later because these notifications are cheap.
     // We will likely only collect once since we are batching collection on
     // a delay.
-    docShell.QueryInterface(Ci.nsIWebNavigation).sessionHistory.
-      addSHistoryListener(this);
+    docShell.QueryInterface(Ci.nsIWebNavigation).
+      sessionHistory.legacySHistory.addSHistoryListener(this);
 
     // Collect data if we start with a non-empty shistory.
     if (!SessionHistory.isEmpty(docShell)) {
@@ -342,7 +342,7 @@ var SessionHistoryListener = {
   uninit() {
     let sessionHistory = docShell.QueryInterface(Ci.nsIWebNavigation).sessionHistory;
     if (sessionHistory) {
-      sessionHistory.removeSHistoryListener(this);
+      sessionHistory.legacySHistory.removeSHistoryListener(this);
     }
   },
 
diff --git a/browser/components/sessionstore/test/browser_705597.js b/browser/components/sessionstore/test/browser_705597.js
index f560d735a6e8..65f7b2e0951f 100644
--- a/browser/components/sessionstore/test/browser_705597.js
+++ b/browser/components/sessionstore/test/browser_705597.js
@@ -24,7 +24,7 @@ function test() {
 
   promiseTabState(tab, tabState).then(() => {
     let sessionHistory = browser.sessionHistory;
-    let entry = sessionHistory.getEntryAtIndex(0, false);
+    let entry = sessionHistory.legacySHistory.getEntryAtIndex(0, false);
     entry.QueryInterface(Ci.nsISHContainer);
 
     whenChildCount(entry, 1, function() {
diff --git a/browser/components/sessionstore/test/browser_707862.js b/browser/components/sessionstore/test/browser_707862.js
index 527743f871c9..d310a043faea 100644
--- a/browser/components/sessionstore/test/browser_707862.js
+++ b/browser/components/sessionstore/test/browser_707862.js
@@ -24,14 +24,14 @@ function test() {
 
   promiseTabState(tab, tabState).then(() => {
     let sessionHistory = browser.sessionHistory;
-    let entry = sessionHistory.getEntryAtIndex(0, false);
+    let entry = sessionHistory.legacySHistory.getEntryAtIndex(0, false);
     entry.QueryInterface(Ci.nsISHContainer);
 
     whenChildCount(entry, 1, function() {
       whenChildCount(entry, 2, function() {
         promiseBrowserLoaded(browser).then(() => {
           let newSessionHistory = browser.sessionHistory;
-          let newEntry = newSessionHistory.getEntryAtIndex(0, false);
+          let newEntry = newSessionHistory.legacySHistory.getEntryAtIndex(0, false);
 
           whenChildCount(newEntry, 0, function() {
             // Make sure that we reset the state.
diff --git a/browser/components/sessionstore/test/browser_async_remove_tab.js b/browser/components/sessionstore/test/browser_async_remove_tab.js
index a7c289496911..bbe72bb58cfd 100644
--- a/browser/components/sessionstore/test/browser_async_remove_tab.js
+++ b/browser/components/sessionstore/test/browser_async_remove_tab.js
@@ -35,7 +35,7 @@ function restoreClosedTabWithValue(rval) {
 function promiseNewLocationAndHistoryEntryReplaced(browser, snippet) {
   return ContentTask.spawn(browser, snippet, async function(codeSnippet) {
     let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
-    let shistory = webNavigation.sessionHistory;
+    let shistory = webNavigation.sessionHistory.legacySHistory;
 
     // Evaluate the snippet that the changes the location.
     // eslint-disable-next-line no-eval
@@ -70,7 +70,7 @@ function promiseHistoryEntryReplacedNonRemote(browser) {
   let {listeners} = promiseHistoryEntryReplacedNonRemote;
 
   return new Promise(resolve => {
-    let shistory = browser.webNavigation.sessionHistory;
+    let shistory = browser.webNavigation.sessionHistory.legacySHistory;
 
     let listener = {
       OnHistoryReplaceEntry() {
diff --git a/browser/components/sessionstore/test/browser_async_window_flushing.js b/browser/components/sessionstore/test/browser_async_window_flushing.js
index c0f69308fb48..258e22f09c9f 100644
--- a/browser/components/sessionstore/test/browser_async_window_flushing.js
+++ b/browser/components/sessionstore/test/browser_async_window_flushing.js
@@ -109,7 +109,7 @@ add_task(async function test_remove_uninteresting_window() {
     docShell.setCurrentURI(Services.io.newURI("about:blank"));
 
     let {sessionHistory} = docShell.QueryInterface(Ci.nsIWebNavigation);
-    sessionHistory.PurgeHistory(sessionHistory.count);
+    sessionHistory.legacySHistory.PurgeHistory(sessionHistory.count);
   });
 
   // Once this windowClosed Promise resolves, we should have finished
diff --git a/browser/components/sessionstore/test/browser_docshell_uuid_consistency.js b/browser/components/sessionstore/test/browser_docshell_uuid_consistency.js
index 01e6b3a30dbc..1837805dacae 100644
--- a/browser/components/sessionstore/test/browser_docshell_uuid_consistency.js
+++ b/browser/components/sessionstore/test/browser_docshell_uuid_consistency.js
@@ -8,7 +8,7 @@ add_task(async function duplicateTab() {
     let docshell = content.window.QueryInterface(Ci.nsIInterfaceRequestor)
                                  .getInterface(Ci.nsIWebNavigation)
                                  .QueryInterface(Ci.nsIDocShell);
-    let shEntry = docshell.sessionHistory.getEntryAtIndex(0, false);
+    let shEntry = docshell.sessionHistory.legacySHistory.getEntryAtIndex(0, false);
     is(shEntry.docshellID.toString(), docshell.historyID.toString());
   });
 
@@ -19,7 +19,7 @@ add_task(async function duplicateTab() {
     let docshell = content.window.QueryInterface(Ci.nsIInterfaceRequestor)
                                  .getInterface(Ci.nsIWebNavigation)
                                  .QueryInterface(Ci.nsIDocShell);
-    let shEntry = docshell.sessionHistory.getEntryAtIndex(0, false);
+    let shEntry = docshell.sessionHistory.legacySHistory.getEntryAtIndex(0, false);
     is(shEntry.docshellID.toString(), docshell.historyID.toString());
   });
 
@@ -39,7 +39,7 @@ add_task(async function contentToChromeNavigate() {
                                  .QueryInterface(Ci.nsIDocShell);
     let sh = docshell.sessionHistory;
     is(sh.count, 1);
-    is(sh.getEntryAtIndex(0, false).docshellID.toString(), docshell.historyID.toString());
+    is(sh.legacySHistory.getEntryAtIndex(0, false).docshellID.toString(), docshell.historyID.toString());
   });
 
   // Force the browser to navigate to the chrome process.
@@ -58,8 +58,8 @@ add_task(async function contentToChromeNavigate() {
   let sh = docShell.QueryInterface(Ci.nsIWebNavigation).sessionHistory;
 
   is(sh.count, 2);
-  is(sh.getEntryAtIndex(0, false).docshellID.toString(), docShell.historyID.toString());
-  is(sh.getEntryAtIndex(1, false).docshellID.toString(), docShell.historyID.toString());
+  is(sh.legacySHistory.getEntryAtIndex(0, false).docshellID.toString(), docShell.historyID.toString());
+  is(sh.legacySHistory.getEntryAtIndex(1, false).docshellID.toString(), docShell.historyID.toString());
 
   BrowserTestUtils.removeTab(tab);
 });
diff --git a/browser/components/sessionstore/test/browser_purge_shistory.js b/browser/components/sessionstore/test/browser_purge_shistory.js
index 09744e67ad6e..2b091d890029 100644
--- a/browser/components/sessionstore/test/browser_purge_shistory.js
+++ b/browser/components/sessionstore/test/browser_purge_shistory.js
@@ -15,7 +15,7 @@ const TAB_STATE = {
 function checkTabContents(browser) {
   return ContentTask.spawn(browser, null, async function() {
     let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
-    let history = webNavigation.sessionHistory.QueryInterface(Ci.nsISHistoryInternal);
+    let history = webNavigation.sessionHistory;
     Assert.ok(history && history.count == 1 && content.document.documentURI == "about:mozilla",
       "expected tab contents found");
   });
diff --git a/browser/components/sessionstore/test/browser_replace_load.js b/browser/components/sessionstore/test/browser_replace_load.js
index 63d30ff15232..7fe87a89fd1f 100644
--- a/browser/components/sessionstore/test/browser_replace_load.js
+++ b/browser/components/sessionstore/test/browser_replace_load.js
@@ -42,7 +42,7 @@ var testSwitchToTab = async function(url, options) {
   // Check that we didn't lose any history entries.
   await ContentTask.spawn(browser, null, async function() {
     let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
-    let history = webNavigation.sessionHistory.QueryInterface(Ci.nsISHistoryInternal);
+    let history = webNavigation.sessionHistory;
     Assert.equal(history && history.count, 3, "three history entries");
   });
 
diff --git a/browser/components/sessionstore/test/browser_switch_remoteness.js b/browser/components/sessionstore/test/browser_switch_remoteness.js
index e83801044f26..9e45c2e8721b 100644
--- a/browser/components/sessionstore/test/browser_switch_remoteness.js
+++ b/browser/components/sessionstore/test/browser_switch_remoteness.js
@@ -5,7 +5,7 @@ const URL = "http://example.com/browser_switch_remoteness_";
 function countHistoryEntries(browser, expected) {
   return ContentTask.spawn(browser, { expected }, async function(args) {
     let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
-    let history = webNavigation.sessionHistory.QueryInterface(Ci.nsISHistoryInternal);
+    let history = webNavigation.sessionHistory;
     Assert.equal(history && history.count, args.expected,
       "correct number of shistory entries");
   });
diff --git a/browser/components/sessionstore/test/content.js b/browser/components/sessionstore/test/content.js
index 9fd1cc42cb29..3897b807c695 100644
--- a/browser/components/sessionstore/test/content.js
+++ b/browser/components/sessionstore/test/content.js
@@ -54,7 +54,7 @@ var historyListener = {
 
 var {sessionHistory} = docShell.QueryInterface(Ci.nsIWebNavigation);
 if (sessionHistory) {
-  sessionHistory.addSHistoryListener(historyListener);
+  sessionHistory.legacySHistory.addSHistoryListener(historyListener);
 }
 
 /**
diff --git a/docshell/test/browser/browser_bug422543.js b/docshell/test/browser/browser_bug422543.js
index 0fcabe99429c..d78851284cac 100644
--- a/docshell/test/browser/browser_bug422543.js
+++ b/docshell/test/browser/browser_bug422543.js
@@ -14,11 +14,11 @@ add_task(async function runTests() {
   ok(browser.canGoBack, "we can go back");
 
   await whenPageShown(browser, () => browser.goBack());
-  await checkListeners("goback", "back to the first shentry");
+  await checkListeners("gotoindex", "back to the first shentry");
   ok(browser.canGoForward, "we can go forward");
 
   await whenPageShown(browser, () => browser.goForward());
-  await checkListeners("goforward", "forward to the second shentry");
+  await checkListeners("gotoindex", "forward to the second shentry");
 
   await whenPageShown(browser, () => browser.reload());
   await checkListeners("reload", "current shentry reloaded");
diff --git a/docshell/test/browser/browser_bug655273.js b/docshell/test/browser/browser_bug655273.js
index ab26cc22b7d6..ec26b7e4e0f8 100644
--- a/docshell/test/browser/browser_bug655273.js
+++ b/docshell/test/browser/browser_bug655273.js
@@ -23,7 +23,7 @@ add_task(async function test() {
                          .getInterface(Ci.nsIWebNavigation)
                          .sessionHistory;
 
-        is(shistory.getEntryAtIndex(shistory.index, false).title,
+        is(shistory.legacySHistory.getEntryAtIndex(shistory.index, false).title,
            oldTitle, 'SHEntry title after pushstate.');
       });
     });
diff --git a/docshell/test/browser/browser_bug670318.js b/docshell/test/browser/browser_bug670318.js
index 39beddfb8a03..ccec831b2884 100644
--- a/docshell/test/browser/browser_bug670318.js
+++ b/docshell/test/browser/browser_bug670318.js
@@ -30,7 +30,7 @@ add_task(async function test() {
               testDone.resolve();
             }, true);
 
-            history.removeSHistoryListener(listener);
+            history.legacySHistory.removeSHistoryListener(listener);
             delete content._testListener;
             content.setTimeout(() => { content.location.reload(); }, 0);
           }
@@ -55,7 +55,7 @@ add_task(async function test() {
                                                Ci.nsISupportsWeakReference])
       };
 
-      history.addSHistoryListener(listener);
+      history.legacySHistory.addSHistoryListener(listener);
       // Since listener implements nsISupportsWeakReference, we are
       // responsible for keeping it alive so that the GC doesn't clear
       // it before the test completes. We do this by anchoring the listener
diff --git a/docshell/test/browser/file_bug422543_script.js b/docshell/test/browser/file_bug422543_script.js
index bf92096650ec..58111f7dfe01 100644
--- a/docshell/test/browser/file_bug422543_script.js
+++ b/docshell/test/browser/file_bug422543_script.js
@@ -50,13 +50,13 @@ let testAPI = {
   init() {
     this.shistory = docShell.QueryInterface(Ci.nsIWebNavigation).sessionHistory;
     for (let listener of this.listeners) {
-      this.shistory.addSHistoryListener(listener);
+      this.shistory.legacySHistory.addSHistoryListener(listener);
     }
   },
 
   cleanup() {
     for (let listener of this.listeners) {
-      this.shistory.removeSHistoryListener(listener);
+      this.shistory.legacySHistory.removeSHistoryListener(listener);
     }
     this.shistory = null;
     sendAsyncMessage("bug422543:cleanup:return", {});
@@ -76,7 +76,7 @@ let testAPI = {
   },
 
   notifyReload() {
-    let internal = this.shistory.QueryInterface(Ci.nsISHistoryInternal);
+    let internal = this.shistory.legacySHistory.QueryInterface(Ci.nsISHistoryInternal);
     let rval =
       internal.notifyOnHistoryReload(content.document.documentURIObject, 0);
     sendAsyncMessage("bug422543:notifyReload:return", { rval });
diff --git a/docshell/test/chrome/bug112564_window.xul b/docshell/test/chrome/bug112564_window.xul
index 0660408a4323..f0a56713d1e2 100644
--- a/docshell/test/chrome/bug112564_window.xul
+++ b/docshell/test/chrome/bug112564_window.xul
@@ -35,7 +35,7 @@
 
       // Work around bug 467960
       var history = gBrowser.webNavigation.sessionHistory;
-      history.PurgeHistory(history.count);
+      history.legacySHistory.PurgeHistory(history.count);
 
       window.close();
       window.opener.wrappedJSObject.SimpleTest.finish();
diff --git a/docshell/test/chrome/bug215405_window.xul b/docshell/test/chrome/bug215405_window.xul
index 9badd5eba5db..ab8445563d2b 100644
--- a/docshell/test/chrome/bug215405_window.xul
+++ b/docshell/test/chrome/bug215405_window.xul
@@ -34,7 +34,7 @@
       gBrowser.removeEventListener("pageshow", eventListener, true);
       // Work around bug 467960
       var history = gBrowser.webNavigation.sessionHistory;
-      history.PurgeHistory(history.count);
+      history.legacySHistory.PurgeHistory(history.count);
 
       window.close();
       window.opener.wrappedJSObject.SimpleTest.finish();
diff --git a/docshell/test/chrome/bug396519_window.xul b/docshell/test/chrome/bug396519_window.xul
index 1e10eeceee47..4e0d3ecff73a 100644
--- a/docshell/test/chrome/bug396519_window.xul
+++ b/docshell/test/chrome/bug396519_window.xul
@@ -59,7 +59,7 @@
       var history = gBrowser.webNavigation.sessionHistory;
       if (history.count == gExpected.length) {
         for (var i=0; i<history.count; i++) {
-          var shEntry = history.getEntryAtIndex(i,false).
+          var shEntry = history.legacySHistory.getEntryAtIndex(i,false).
                           QueryInterface(Ci.nsISHEntry);
           is(!!shEntry.contentViewer, gExpected[i], "content viewer "+i+", test "+gTestCount);
         }
@@ -71,9 +71,9 @@
             if (j == i)
               continue;
 
-            let shentry1 = history.getEntryAtIndex(i, false)
+            let shentry1 = history.legacySHistory.getEntryAtIndex(i, false)
                                   .QueryInterface(Ci.nsISHEntry);
-            let shentry2 = history.getEntryAtIndex(j, false)
+            let shentry2 = history.legacySHistory.getEntryAtIndex(j, false)
                                   .QueryInterface(Ci.nsISHEntry);
             ok(!shentry1.sharesDocumentWith(shentry2),
                'Test ' + gTestCount + ': shentry[' + i + "] shouldn't " +
diff --git a/docshell/test/chrome/bug92598_window.xul b/docshell/test/chrome/bug92598_window.xul
index 5d22b7abe3cd..9dba73f39861 100644
--- a/docshell/test/chrome/bug92598_window.xul
+++ b/docshell/test/chrome/bug92598_window.xul
@@ -35,7 +35,7 @@
      
       // Work around bug 467960
       var history = gBrowser.webNavigation.sessionHistory;
-      history.PurgeHistory(history.count);
+      history.legacySHistory.PurgeHistory(history.count);
 
       window.close();
       window.opener.wrappedJSObject.SimpleTest.finish();
diff --git a/docshell/test/chrome/docshell_helpers.js b/docshell/test/chrome/docshell_helpers.js
index 9bef9c03d353..72f4179e1e1e 100755
--- a/docshell/test/chrome/docshell_helpers.js
+++ b/docshell/test/chrome/docshell_helpers.js
@@ -341,7 +341,7 @@ function pageEventListener(event) {
 function finish() {
   // Work around bug 467960.
   var history = TestWindow.getBrowser().webNavigation.sessionHistory;
-  history.PurgeHistory(history.count);
+  history.legacySHistory.PurgeHistory(history.count);
   
   // If the test changed the value of max_total_viewers via a call to
   // enableBFCache(), then restore it now.
diff --git a/docshell/test/navigation/file_bug1300461.html b/docshell/test/navigation/file_bug1300461.html
index 1ba935046d7d..790a90d54ed6 100644
--- a/docshell/test/navigation/file_bug1300461.html
+++ b/docshell/test/navigation/file_bug1300461.html
@@ -40,7 +40,7 @@
           opener.is(shistory.index, 0, 'check history index');
           opener.ok(webNav.canGoForward, 'check canGoForward');
           window.history.forward();
-          opener.is(shistory.requestedIndex, 1, 'check requestedIndex');
+          opener.is(shistory.legacySHistory.requestedIndex, 1, 'check requestedIndex');
         },
         function() {
           opener.is(shistory.count, 2, 'check history length');
diff --git a/docshell/test/navigation/file_bug1300461_back.html b/docshell/test/navigation/file_bug1300461_back.html
index 7b187742faeb..84ab034aba16 100644
--- a/docshell/test/navigation/file_bug1300461_back.html
+++ b/docshell/test/navigation/file_bug1300461_back.html
@@ -17,7 +17,7 @@
           opener.info("file_bug1300461_back.html");
           opener.is(shistory.count, 2, 'check history length');
           opener.is(shistory.index, 1, 'check history index');
-          opener.is(shistory.requestedIndex, -1, 'check requestedIndex');
+          opener.is(shistory.legacySHistory.requestedIndex, -1, 'check requestedIndex');
           opener.ok(webNav.canGoBack, 'check canGoBack');
           if (opener.testCount == 1) {
             opener.info('replaceState to redirect.html');
diff --git a/docshell/test/navigation/file_bug1326251_evict_cache.html b/docshell/test/navigation/file_bug1326251_evict_cache.html
index c546d5cfd345..e99b870ea8fe 100644
--- a/docshell/test/navigation/file_bug1326251_evict_cache.html
+++ b/docshell/test/navigation/file_bug1326251_evict_cache.html
@@ -12,7 +12,7 @@
                        .QueryInterface(SpecialPowers.Ci.nsIInterfaceRequestor)
                        .getInterface(SpecialPowers.Ci.nsIWebNavigation)
                        .sessionHistory;
-      let shPrivate = shistory.QueryInterface(SpecialPowers.Ci.nsISHistoryInternal);
+      let shPrivate = shistory.legacySHistory.QueryInterface(SpecialPowers.Ci.nsISHistoryInternal);
       shPrivate.evictAllContentViewers();
       history.back();
     }
diff --git a/docshell/test/navigation/test_bug1375833.html b/docshell/test/navigation/test_bug1375833.html
index d0af4d994748..d6653e012a2c 100644
--- a/docshell/test/navigation/test_bug1375833.html
+++ b/docshell/test/navigation/test_bug1375833.html
@@ -49,7 +49,7 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1375833
       ok(newFrameDocShellId, "sanity check for docshell ID");
       is(newFrameDocShellId, frameDocShellId, "check docshell ID remains after reload");
 
-      let entry = shistory.getEntryAtIndex(shistory.index, false);
+      let entry = shistory.legacySHistory.getEntryAtIndex(shistory.index, false);
       let frameEntry = SpecialPowers.wrap(entry)
                        .QueryInterface(SpecialPowers.Ci.nsISHContainer)
                        .GetChildAt(0);
diff --git a/docshell/test/test_bug509055.html b/docshell/test/test_bug509055.html
index 28f520fdafca..d8b78196f38e 100644
--- a/docshell/test/test_bug509055.html
+++ b/docshell/test/test_bug509055.html
@@ -75,8 +75,8 @@ function* runTest() {
                         .getInterface(SpecialPowers.Ci.nsIWebNavigation)
                         .sessionHistory;
 
-  // Get the title of the inner popup's current SHEntry 
-  var sheTitle = sh.getEntryAtIndex(sh.index, false).title;
+  // Get the title of the inner popup's current SHEntry
+  var sheTitle = sh.legacySHistory.getEntryAtIndex(sh.index, false).title;
   is(sheTitle, "Changed", "SHEntry's title should change when we change.");
 
   popup.close();
diff --git a/docshell/test/test_bug590573.html b/docshell/test/test_bug590573.html
index ad810413afba..c010cef842a3 100644
--- a/docshell/test/test_bug590573.html
+++ b/docshell/test/test_bug590573.html
@@ -106,10 +106,10 @@ function dumpSHistory(theWindow)
 
   dump(" count: " + sh.count + "\n");
   dump(" index: " + sh.index + "\n");
-  dump(" requestedIndex: " + sh.requestedIndex + "\n");
+  dump(" requestedIndex: " + sh.legacySHistory.requestedIndex + "\n");
 
   for (let i = 0; i < sh.count; i++) {
-    let shentry = sh.getEntryAtIndex(i, false);
+    let shentry = sh.legacySHistory.getEntryAtIndex(i, false);
     dump(" " + i + ": " + shentry.URI.spec + '\n');
     shentry.QueryInterface(SpecialPowers.Ci.nsISHContainer);
     for (let j = 0; j < shentry.childCount; j++) {
diff --git a/dom/browser-element/BrowserElementChildPreload.js b/dom/browser-element/BrowserElementChildPreload.js
index c5d3b9b034d6..94770ed89b1a 100644
--- a/dom/browser-element/BrowserElementChildPreload.js
+++ b/dom/browser-element/BrowserElementChildPreload.js
@@ -139,7 +139,9 @@ BrowserElementChild.prototype = {
 
     let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
     if (!webNavigation.sessionHistory) {
-      // XXX(nika): We might need to start this up some other way?
+      // XXX(nika): I don't think this code should ever be hit? We should run
+      // TabChild::Init before we run this code which will perform this setup
+      // for us.
       docShell.initSessionHistory();
     }
 
@@ -919,7 +921,7 @@ BrowserElementChild.prototype = {
 
     try {
       if (history && history.count) {
-        history.PurgeHistory(history.count);
+        history.legacySHistory.PurgeHistory(history.count);
       }
     } catch(e) {}
 
diff --git a/dom/html/test/browser_bug649778.js b/dom/html/test/browser_bug649778.js
index c87cb89fa338..7a18f091f105 100644
--- a/dom/html/test/browser_bug649778.js
+++ b/dom/html/test/browser_bug649778.js
@@ -43,7 +43,7 @@ function getPopupURL() {
                 .getInterface(Ci.nsIWebNavigation)
                 .sessionHistory;
 
-  return sh.getEntryAtIndex(sh.index, false).URI.spec;
+  return sh.legacySHistory.getEntryAtIndex(sh.index, false).URI.spec;
 }
 
 var wyciwygURL;
diff --git a/dom/tests/mochitest/whatwg/test_bug500328.html b/dom/tests/mochitest/whatwg/test_bug500328.html
index 31f739ab86a0..3b8e315ea15b 100644
--- a/dom/tests/mochitest/whatwg/test_bug500328.html
+++ b/dom/tests/mochitest/whatwg/test_bug500328.html
@@ -177,7 +177,7 @@ function getSHTitle(sh, offset)
     offset = 0;
 
   // False instructs the SHistory not to modify its current index.
-  return sh.getEntryAtIndex(sh.index + offset, false).title;
+  return sh.legacySHistory.getEntryAtIndex(sh.index + offset, false).title;
 }
 
 // Tests that win's location ends with str
diff --git a/mobile/android/chrome/content/browser.js b/mobile/android/chrome/content/browser.js
index 0cc5e6e394a9..ce88b6d5e4e0 100644
--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -1884,7 +1884,7 @@ var BrowserApp = {
         try {
           let sh = webNav.sessionHistory;
           if (sh)
-            webNav = sh.QueryInterface(Ci.nsIWebNavigation);
+            webNav = sh.legacySHistory.QueryInterface(Ci.nsIWebNavigation);
         } catch (e) {}
         webNav.reload(flags);
         break;
@@ -2240,7 +2240,7 @@ var BrowserApp = {
     }
 
     let browser = this.selectedBrowser;
-    let hist = browser.sessionHistory;
+    let hist = browser.sessionHistory.legacySHistory;
     for (let i = toIndex; i >= fromIndex; i--) {
       let entry = hist.getEntryAtIndex(i, false);
       let item = {
@@ -3718,7 +3718,7 @@ Tab.prototype = {
     this.filter = Cc["@mozilla.org/appshell/component/browser-status-filter;1"].createInstance(Ci.nsIWebProgress);
     this.filter.addProgressListener(this, flags)
     this.browser.addProgressListener(this.filter, flags);
-    this.browser.sessionHistory.addSHistoryListener(this);
+    this.browser.sessionHistory.legacySHistory.addSHistoryListener(this);
 
     this.browser.addEventListener("DOMContentLoaded", this, true);
     this.browser.addEventListener("DOMFormHasPassword", this, true);
@@ -3842,7 +3842,7 @@ Tab.prototype = {
     this.browser.removeProgressListener(this.filter);
     this.filter.removeProgressListener(this);
     this.filter = null;
-    this.browser.sessionHistory.removeSHistoryListener(this);
+    this.browser.sessionHistory.legacySHistory.removeSHistoryListener(this);
 
     this.browser.removeEventListener("DOMContentLoaded", this, true);
     this.browser.removeEventListener("DOMFormHasPassword", this, true);
diff --git a/testing/firefox-ui/tests/puppeteer/test_toolbars.py b/testing/firefox-ui/tests/puppeteer/test_toolbars.py
index 8ee6e23e8217..e4c935da0dce 100644
--- a/testing/firefox-ui/tests/puppeteer/test_toolbars.py
+++ b/testing/firefox-ui/tests/puppeteer/test_toolbars.py
@@ -22,7 +22,7 @@ class TestNavBar(PuppeteerMixin, MarionetteTestCase):
         # TODO: check why self.puppeteer.places.remove_all_history() does not work here
         self.marionette.execute_script("""
             let count = gBrowser.sessionHistory.count;
-            gBrowser.sessionHistory.PurgeHistory(count);
+            gBrowser.sessionHistory.legacySHistory.PurgeHistory(count);
         """)
 
     def test_elements(self):
diff --git a/toolkit/components/reader/ReaderMode.jsm b/toolkit/components/reader/ReaderMode.jsm
index b2ba9e303813..6d39db34e1a3 100644
--- a/toolkit/components/reader/ReaderMode.jsm
+++ b/toolkit/components/reader/ReaderMode.jsm
@@ -102,7 +102,7 @@ var ReaderMode = {
     let webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
     let sh = webNav.sessionHistory;
     if (webNav.canGoForward) {
-      let forwardEntry = sh.getEntryAtIndex(sh.index + 1, false);
+      let forwardEntry = sh.legacySHistory.getEntryAtIndex(sh.index + 1, false);
       let forwardURL = forwardEntry.URI.spec;
       if (forwardURL && (forwardURL == readerURL || !readerURL)) {
         webNav.goForward();
@@ -123,7 +123,7 @@ var ReaderMode = {
     let webNav = docShell.QueryInterface(Ci.nsIWebNavigation);
     let sh = webNav.sessionHistory;
     if (webNav.canGoBack) {
-      let prevEntry = sh.getEntryAtIndex(sh.index - 1, false);
+      let prevEntry = sh.legacySHistory.getEntryAtIndex(sh.index - 1, false);
       let prevURL = prevEntry.URI.spec;
       if (prevURL && (prevURL == originalURL || !originalURL)) {
         webNav.goBack();
diff --git a/toolkit/components/viewsource/content/viewSource-content.js b/toolkit/components/viewsource/content/viewSource-content.js
index d623db35fb22..e0fb3bd460a1 100644
--- a/toolkit/components/viewsource/content/viewSource-content.js
+++ b/toolkit/components/viewsource/content/viewSource-content.js
@@ -270,6 +270,7 @@ var ViewSourceContent = {
     shEntry.cacheKey = shEntrySource.cacheKey;
     docShell.QueryInterface(Ci.nsIWebNavigation)
             .sessionHistory
+            .legacySHistory
             .QueryInterface(Ci.nsISHistoryInternal)
             .addEntry(shEntry, true);
   },
diff --git a/toolkit/content/browser-content.js b/toolkit/content/browser-content.js
index 5071c0e8f066..b67b54a9194a 100644
--- a/toolkit/content/browser-content.js
+++ b/toolkit/content/browser-content.js
@@ -1277,10 +1277,11 @@ addMessageListener("Browser:PurgeSessionHistory", function BrowserPurgeHistory()
 
   // place the entry at current index at the end of the history list, so it won't get removed
   if (sessionHistory.index < sessionHistory.count - 1) {
-    let indexEntry = sessionHistory.getEntryAtIndex(sessionHistory.index, false);
-    sessionHistory.QueryInterface(Ci.nsISHistoryInternal);
+    let legacy = sessionHistory.legacySHistory;
+    legacy.QueryInterface(Ci.nsISHistoryInternal);
+    let indexEntry = legacy.getEntryAtIndex(sessionHistory.index, false);
     indexEntry.QueryInterface(Ci.nsISHEntry);
-    sessionHistory.addEntry(indexEntry, true);
+    legacy.addEntry(indexEntry, true);
   }
 
   let purge = sessionHistory.count;
@@ -1289,7 +1290,7 @@ addMessageListener("Browser:PurgeSessionHistory", function BrowserPurgeHistory()
   }
 
   if (purge > 0) {
-    sessionHistory.PurgeHistory(purge);
+    sessionHistory.legacySHistory.PurgeHistory(purge);
   }
 });
 
diff --git a/toolkit/modules/E10SUtils.jsm b/toolkit/modules/E10SUtils.jsm
index e1b61c0741a8..5b0763a8e04c 100644
--- a/toolkit/modules/E10SUtils.jsm
+++ b/toolkit/modules/E10SUtils.jsm
@@ -224,9 +224,9 @@ var E10SUtils = {
     // Allow history load if loaded in this process before.
     let webNav = aDocShell.QueryInterface(Ci.nsIWebNavigation);
     let sessionHistory = webNav.sessionHistory;
-    let requestedIndex = sessionHistory.requestedIndex;
+    let requestedIndex = sessionHistory.legacySHistory.requestedIndex;
     if (requestedIndex >= 0) {
-      if (sessionHistory.getEntryAtIndex(requestedIndex, false).loadedInThisProcess) {
+      if (sessionHistory.legacySHistory.getEntryAtIndex(requestedIndex, false).loadedInThisProcess) {
         return true;
       }
 
@@ -265,7 +265,7 @@ var E10SUtils = {
                              : null,
         reloadInFreshProcess: !!aFreshProcess,
       },
-      historyIndex: sessionHistory.requestedIndex,
+      historyIndex: sessionHistory.legacySHistory.requestedIndex,
     });
     return false;
   },
diff --git a/toolkit/modules/sessionstore/SessionHistory.jsm b/toolkit/modules/sessionstore/SessionHistory.jsm
index 3aa3d21f7a30..3d754ec715f5 100644
--- a/toolkit/modules/sessionstore/SessionHistory.jsm
+++ b/toolkit/modules/sessionstore/SessionHistory.jsm
@@ -72,7 +72,7 @@ var SessionHistoryInternal = {
   collect(docShell, aFromIdx = -1) {
     let loadContext = docShell.QueryInterface(Ci.nsILoadContext);
     let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
-    let history = webNavigation.sessionHistory.QueryInterface(Ci.nsISHistoryInternal);
+    let history = webNavigation.sessionHistory;
 
     let data = {entries: [], userContextId: loadContext.originAttributes.userContextId };
     // We want to keep track how many entries we *could* have collected and
@@ -83,7 +83,8 @@ var SessionHistoryInternal = {
     if (history && history.count > 0) {
       // Loop over the transaction linked list directly so we can get the
       // persist property for each transaction.
-      for (let txn = history.rootTransaction; txn; entryCount++, txn = txn.next) {
+      for (let txn = history.legacySHistory.QueryInterface(Ci.nsISHistoryInternal).rootTransaction;
+           txn; entryCount++, txn = txn.next) {
         if (entryCount <= aFromIdx) {
           skippedCount++;
           continue;
@@ -317,7 +318,7 @@ var SessionHistoryInternal = {
    */
   restore(docShell, tabData) {
     let webNavigation = docShell.QueryInterface(Ci.nsIWebNavigation);
-    let history = webNavigation.sessionHistory;
+    let history = webNavigation.sessionHistory.legacySHistory;
     if (history.count > 0) {
       history.PurgeHistory(history.count);
     }