diff -r 000000000000 -r 6474c204b198 mobile/android/base/toolbar/ToolbarTitlePrefs.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mobile/android/base/toolbar/ToolbarTitlePrefs.java	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,99 @@
+/* -*- Mode: Java; c-basic-offset: 4; tab-width: 20; indent-tabs-mode: nil; -*-
+ * 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/. */
+
+package org.mozilla.gecko.toolbar;
+
+import org.mozilla.gecko.PrefsHelper;
+import org.mozilla.gecko.Tab;
+import org.mozilla.gecko.Tabs;
+import org.mozilla.gecko.util.ThreadUtils;
+
+class ToolbarTitlePrefs {
+    static final String PREF_TITLEBAR_MODE = "browser.chrome.titlebarMode";
+    static final String PREF_TRIM_URLS = "browser.urlbar.trimURLs";
+
+    interface OnChangeListener {
+        public void onChange();
+    }
+
+    final String[] prefs = {
+        PREF_TITLEBAR_MODE,
+        PREF_TRIM_URLS
+    };
+
+    private boolean mShowUrl;
+    private boolean mTrimUrls;
+
+    private Integer mPrefObserverId;
+
+    ToolbarTitlePrefs() {
+        mShowUrl = false;
+        mTrimUrls = true;
+
+        mPrefObserverId = PrefsHelper.getPrefs(prefs, new TitlePrefsHandler());
+    }
+
+    boolean shouldShowUrl() {
+        return mShowUrl;
+    }
+
+    boolean shouldTrimUrls() {
+        return mTrimUrls;
+    }
+
+    void close() {
+        if (mPrefObserverId != null) {
+             PrefsHelper.removeObserver(mPrefObserverId);
+             mPrefObserverId = null;
+        }
+    }
+
+    private class TitlePrefsHandler extends PrefsHelper.PrefHandlerBase {
+        @Override
+        public void prefValue(String pref, String str) {
+            // Handles PREF_TITLEBAR_MODE, which is always a string.
+            int value = Integer.parseInt(str);
+            boolean shouldShowUrl = (value == 1);
+
+            if (shouldShowUrl == mShowUrl) {
+                return;
+            }
+            mShowUrl = shouldShowUrl;
+
+            triggerChangeListener();
+        }
+
+        @Override
+        public void prefValue(String pref, boolean value) {
+            // Handles PREF_TRIM_URLS, which should usually be a boolean.
+            if (value == mTrimUrls) {
+                return;
+            }
+            mTrimUrls = value;
+
+            triggerChangeListener();
+        }
+
+        @Override
+        public boolean isObserver() {
+            // We want to be notified of changes to be able to switch mode
+            // without restarting.
+            return true;
+        }
+
+        private void triggerChangeListener() {
+            ThreadUtils.postToUiThread(new Runnable() {
+                @Override
+                public void run() {
+                    final Tabs tabs = Tabs.getInstance();
+                    final Tab tab = tabs.getSelectedTab();
+                    if (tab != null) {
+                        tabs.notifyListeners(tab, Tabs.TabEvents.TITLE);
+                    }
+                }
+            });
+        }
+    }
+}