--- a/mobile/android/base/preferences/GeckoPreferenceFragment.java
+++ b/mobile/android/base/preferences/GeckoPreferenceFragment.java
@@ -15,16 +15,17 @@ import android.preference.Preference;
 import android.preference.PreferenceActivity;
 import android.preference.PreferenceCategory;
 import android.preference.PreferenceFragment;
 import android.preference.PreferenceScreen;
 import android.os.Bundle;
 import android.util.Log;
 import android.view.Menu;
 import android.view.MenuInflater;
+import android.view.MenuItem;
 import android.view.ViewConfiguration;
 
 /* A simple implementation of PreferenceFragment for large screen devices
  * This will strip category headers (so that they aren't shown to the user twice)
  * as well as initializing Gecko prefs when a fragment is shown.
 */
 public class GeckoPreferenceFragment extends PreferenceFragment {
 

--- a/mobile/android/base/preferences/GeckoPreferences.java
+++ b/mobile/android/base/preferences/GeckoPreferences.java
@@ -72,17 +72,19 @@ public class GeckoPreferences
     private static final String NON_PREF_PREFIX = "android.not_a_preference.";
     public static final String INTENT_EXTRA_RESOURCES = "resource";
     public static String PREFS_HEALTHREPORT_UPLOAD_ENABLED = NON_PREF_PREFIX + "healthreport.uploadEnabled";
 
     private static boolean sIsCharEncodingEnabled = false;
     private boolean mInitialized = false;
     private int mPrefsRequestId = 0;
 
-    // These match keys in resources/xml/preferences.xml.in.
+    // These match keys in resources/xml*/preferences*.xml
+    private static String PREFS_SEARCH_RESTORE_DEFAULTS = NON_PREF_PREFIX + "search.restore_defaults";
+
     private static String PREFS_ANNOUNCEMENTS_ENABLED = NON_PREF_PREFIX + "privacy.announcements.enabled";
     private static String PREFS_DATA_REPORTING_PREFERENCES = NON_PREF_PREFIX + "datareporting.preferences";
     private static String PREFS_TELEMETRY_ENABLED = "datareporting.telemetry.enabled";
     private static String PREFS_CRASHREPORTER_ENABLED = "datareporting.crashreporter.submitEnabled";
     private static String PREFS_MENU_CHAR_ENCODING = "browser.menu.showCharacterEncoding";
     private static String PREFS_MP_ENABLED = "privacy.masterpassword.enabled";
     private static String PREFS_UPDATER_AUTODOWNLOAD = "app.update.autodownload";
     private static String PREFS_GEO_REPORTING = "app.geo.reportdata";
@@ -384,39 +386,64 @@ public class GeckoPreferences
                     CharSequence selectedEntry = listPref.getEntry();
                     listPref.setSummary(selectedEntry);
                     continue;
                 } else if (PREFS_SYNC.equals(key) && GeckoProfile.get(this).inGuestMode()) {
                     // Don't show sync prefs while in guest mode.
                     preferences.removePreference(pref);
                     i--;
                     continue;
+                } else if (PREFS_SEARCH_RESTORE_DEFAULTS.equals(key)) {
+                    pref.setOnPreferenceClickListener(new OnPreferenceClickListener() {
+                        @Override
+                        public boolean onPreferenceClick(Preference preference) {
+                            GeckoPreferences.this.restoreDefaultSearchEngines();
+                            return true;
+                        }
+                    });
                 }
 
                 // Some Preference UI elements are not actually preferences,
                 // but they require a key to work correctly. For example,
                 // "Clear private data" requires a key for its state to be
                 // saved when the orientation changes. It uses the
                 // "android.not_a_preference.privacy.clear" key - which doesn't
                 // exist in Gecko - to satisfy this requirement.
                 if (key != null && !key.startsWith(NON_PREF_PREFIX)) {
                     prefs.add(key);
                 }
             }
         }
     }
 
+    /**
+     * Restore default search engines in Gecko and retrigger a search engine refresh.
+     */
+    protected void restoreDefaultSearchEngines() {
+        GeckoAppShell.sendEventToGecko(GeckoEvent.createBroadcastEvent("SearchEngines:RestoreDefaults", null));
+
+        // Send message to Gecko to get engines. SearchPreferenceCategory listens for the response.
+        GeckoAppShell.sendEventToGecko(GeckoEvent.createBroadcastEvent("SearchEngines:GetVisible", null));
+    }
+
     @Override
     public boolean onOptionsItemSelected(MenuItem item) {
-        switch (item.getItemId()) {
+        int itemId = item.getItemId();
+        switch (itemId) {
             case android.R.id.home:
                 finish();
                 return true;
         }
 
+        // Generated R.id.* apparently aren't constant expressions, so they can't be switched.
+        if (itemId == R.id.restore_defaults) {
+            restoreDefaultSearchEngines();
+            return true;
+       }
+
         return super.onOptionsItemSelected(item);
     }
 
     final private int DIALOG_CREATE_MASTER_PASSWORD = 0;
     final private int DIALOG_REMOVE_MASTER_PASSWORD = 1;
 
     public static void setCharEncodingState(boolean enabled) {
         sIsCharEncodingEnabled = enabled;

--- a/mobile/android/base/preferences/SearchPreferenceCategory.java
+++ b/mobile/android/base/preferences/SearchPreferenceCategory.java
@@ -38,37 +38,41 @@ public class SearchPreferenceCategory ex
 
     @Override
     protected void onAttachedToActivity() {
         super.onAttachedToActivity();
 
         // Ensures default engine remains at top of list.
         setOrderingAsAdded(true);
 
-        // Request list of search engines from Gecko.
+        // Register for SearchEngines messages and request list of search engines from Gecko.
         GeckoAppShell.registerEventListener("SearchEngines:Data", this);
         GeckoAppShell.sendEventToGecko(GeckoEvent.createBroadcastEvent("SearchEngines:GetVisible", null));
     }
 
     @Override
+    protected void onPrepareForRemoval() {
+        GeckoAppShell.unregisterEventListener("SearchEngines:Data", this);
+    }
+
+    @Override
     public void handleMessage(String event, final JSONObject data) {
         if (event.equals("SearchEngines:Data")) {
-            // We are no longer interested in this event from Gecko, as we do not request it again with
-            // this instance.
-            GeckoAppShell.unregisterEventListener("SearchEngines:Data", this);
-
             // Parse engines array from JSON.
             JSONArray engines;
             try {
                 engines = data.getJSONArray("searchEngines");
             } catch (JSONException e) {
                 Log.e(LOGTAG, "Unable to decode search engine data from Gecko.", e);
                 return;
             }
 
+            // Clear the preferences category from this thread.
+            this.removeAll();
+
             // Create an element in this PreferenceCategory for each engine.
             for (int i = 0; i < engines.length(); i++) {
                 try {
                     JSONObject engineJSON = engines.getJSONObject(i);
                     final String engineName = engineJSON.getString("name");
 
                     SearchEnginePreference enginePreference = new SearchEnginePreference(getContext(), this);
                     enginePreference.setSearchEngineFromJSON(engineJSON);

--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -6604,18 +6604,19 @@ OverscrollController.prototype = {
 var SearchEngines = {
   _contextMenuId: null,
   PREF_SUGGEST_ENABLED: "browser.search.suggest.enabled",
   PREF_SUGGEST_PROMPTED: "browser.search.suggest.prompted",
 
   init: function init() {
     Services.obs.addObserver(this, "SearchEngines:Add", false);
     Services.obs.addObserver(this, "SearchEngines:GetVisible", false);
+    Services.obs.addObserver(this, "SearchEngines:Remove", false);
+    Services.obs.addObserver(this, "SearchEngines:RestoreDefaults", false);
     Services.obs.addObserver(this, "SearchEngines:SetDefault", false);
-    Services.obs.addObserver(this, "SearchEngines:Remove", false);
 
     let filter = {
       matches: function (aElement) {
         // Copied from body of isTargetAKeywordField function in nsContextMenu.js
         if(!(aElement instanceof HTMLInputElement))
           return false;
         let form = aElement.form;
         if (!form || aElement.type == "password")
@@ -6646,18 +6647,19 @@ var SearchEngines = {
         SearchEngines.addEngine(aElement);
       }
     }
   },
 
   uninit: function uninit() {
     Services.obs.removeObserver(this, "SearchEngines:Add");
     Services.obs.removeObserver(this, "SearchEngines:GetVisible");
+    Services.obs.removeObserver(this, "SearchEngines:Remove");
+    Services.obs.removeObserver(this, "SearchEngines:RestoreDefaults");
     Services.obs.removeObserver(this, "SearchEngines:SetDefault");
-    Services.obs.removeObserver(this, "SearchEngines:Remove");
     if (this._contextMenuId != null)
       NativeWindow.contextmenus.remove(this._contextMenuId);
   },
 
   // Fetch list of search engines. all ? All engines : Visible engines only.
   _handleSearchEnginesGetVisible: function _handleSearchEnginesGetVisible(rv) {
     if (!Components.isSuccessCode(rv)) {
       Cu.reportError("Could not initialize search service, bailing out.");
@@ -6717,29 +6719,34 @@ var SearchEngines = {
     let engine;
     switch(aTopic) {
       case "SearchEngines:Add":
         this.displaySearchEnginesList(aData);
         break;
       case "SearchEngines:GetVisible":
         Services.search.init(this._handleSearchEnginesGetVisible.bind(this));
         break;
-      case "SearchEngines:SetDefault":
-        engine = this._extractEngineFromJSON(aData);
-        // Move the new default search engine to the top of the search engine list.
-        Services.search.moveEngine(engine, 0);
-        Services.search.defaultEngine = engine;
-        break;
       case "SearchEngines:Remove":
         // Make sure the engine isn't hidden before removing it, to make sure it's
         // visible if the user later re-adds it (works around bug 341833)
         engine = this._extractEngineFromJSON(aData);
         engine.hidden = false;
         Services.search.removeEngine(engine);
         break;
+      case "SearchEngines:RestoreDefaults":
+        // Un-hides all default engines.
+        Services.search.restoreDefaultEngines();
+        break;
+      case "SearchEngines:SetDefault":
+        engine = this._extractEngineFromJSON(aData);
+        // Move the new default search engine to the top of the search engine list.
+        Services.search.moveEngine(engine, 0);
+        Services.search.defaultEngine = engine;
+        break;
+
       default:
         dump("Unexpected message type observed: " + aTopic);
         break;
     }
   },
 
   // Display context menu listing names of the search engines available to be added.
   displaySearchEnginesList: function displaySearchEnginesList(aData) {