--- a/mobile/android/base/java/org/mozilla/gecko/FindInPageBar.java
+++ b/mobile/android/base/java/org/mozilla/gecko/FindInPageBar.java
@@ -1,40 +1,40 @@
 /* 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;
 
-import org.mozilla.gecko.util.GeckoEventListener;
-import org.mozilla.gecko.util.GeckoRequest;
+import org.mozilla.gecko.util.BundleEventListener;
+import org.mozilla.gecko.util.EventCallback;
+import org.mozilla.gecko.util.GeckoBundle;
 import org.mozilla.gecko.util.NativeJSObject;
 import org.mozilla.gecko.util.ThreadUtils;
 
-import org.json.JSONObject;
-
 import android.content.Context;
 import android.text.Editable;
 import android.text.TextUtils;
 import android.text.TextWatcher;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.KeyEvent;
 import android.view.LayoutInflater;
 import android.view.View;
 import android.view.inputmethod.InputMethodManager;
 import android.widget.LinearLayout;
 import android.widget.TextView;
 
-public class FindInPageBar extends LinearLayout implements TextWatcher, View.OnClickListener, GeckoEventListener  {
+public class FindInPageBar extends LinearLayout
+        implements TextWatcher, View.OnClickListener, BundleEventListener {
     private static final String LOGTAG = "GeckoFindInPageBar";
     private static final String REQUEST_ID = "FindInPageBar";
 
     private final Context mContext;
-    private CustomEditText mFindText;
+    /* package */ CustomEditText mFindText;
     private TextView mStatusText;
     private boolean mInflated;
 
     public FindInPageBar(Context context, AttributeSet attrs) {
         super(context, attrs);
         mContext = context;
         setFocusable(true);
     }
@@ -62,31 +62,42 @@ public class FindInPageBar extends Linea
                 }
                 return false;
             }
         });
 
         mStatusText = (TextView) content.findViewById(R.id.find_status);
 
         mInflated = true;
-        EventDispatcher.getInstance().registerGeckoThreadListener(this,
-            "FindInPage:MatchesCountResult",
-            "TextSelection:Data");
+        EventDispatcher.getInstance().registerUiThreadListener(this,
+            "FindInPage:MatchesCountResult");
     }
 
     public void show() {
         if (!mInflated)
             inflateContent();
 
         setVisibility(VISIBLE);
         mFindText.requestFocus();
 
         // handleMessage() receives response message and determines initial state of softInput
-        GeckoAppShell.notifyObservers("TextSelection:Get", REQUEST_ID);
-        GeckoAppShell.notifyObservers("FindInPage:Opened", null);
+
+        GeckoApp.getEventDispatcher().dispatch("TextSelection:Get", null, new EventCallback() {
+            @Override
+            public void sendSuccess(final Object result) {
+                onTextSelectionData((String) result);
+            }
+
+            @Override
+            public void sendError(final Object error) {
+                Log.e(LOGTAG, "TextSelection:Get failed: " + error);
+            }
+        });
+
+        EventDispatcher.getInstance().dispatch("FindInPage:Opened", null);
     }
 
     public void hide() {
         if (!mInflated || getVisibility() == View.GONE) {
             // There's nothing to hide yet.
             return;
         }
 
@@ -95,31 +106,30 @@ public class FindInPageBar extends Linea
 
         // Only close the IMM if its EditText is the one with focus.
         if (mFindText.isFocused()) {
           getInputMethodManager(mFindText).hideSoftInputFromWindow(mFindText.getWindowToken(), 0);
         }
 
         // Close the FIPB / FindHelper state.
         setVisibility(GONE);
-        GeckoAppShell.notifyObservers("FindInPage:Closed", null);
+        EventDispatcher.getInstance().dispatch("FindInPage:Closed", null);
     }
 
     private InputMethodManager getInputMethodManager(View view) {
         Context context = view.getContext();
         return (InputMethodManager) context.getSystemService(Context.INPUT_METHOD_SERVICE);
      }
 
     public void onDestroy() {
         if (!mInflated) {
             return;
         }
-        EventDispatcher.getInstance().unregisterGeckoThreadListener(this,
-            "FindInPage:MatchesCountResult",
-            "TextSelection:Data");
+        EventDispatcher.getInstance().unregisterUiThreadListener(this,
+            "FindInPage:MatchesCountResult");
     }
 
     private void onMatchesCountResult(final int total, final int current, final int limit, final String searchString) {
         if (total == -1) {
             updateResult(Integer.toString(limit) + "+");
         } else if (total > 0) {
             updateResult(Integer.toString(current) + "/" + Integer.toString(total));
         } else if (TextUtils.isEmpty(searchString)) {
@@ -128,23 +138,18 @@ public class FindInPageBar extends Linea
             // We display 0/0, when there were no
             // matches found, or if matching has been turned off by setting
             // pref accessibility.typeaheadfind.matchesCountLimit to 0.
             updateResult("0/0");
         }
     }
 
     private void updateResult(final String statusText) {
-        ThreadUtils.postToUiThread(new Runnable() {
-            @Override
-            public void run() {
-                mStatusText.setVisibility(statusText.isEmpty() ? View.GONE : View.VISIBLE);
-                mStatusText.setText(statusText);
-            }
-        });
+        mStatusText.setVisibility(statusText.isEmpty() ? View.GONE : View.VISIBLE);
+        mStatusText.setText(statusText);
     }
 
     // TextWatcher implementation
 
     @Override
     public void afterTextChanged(Editable s) {
         sendRequestToFinderHelper("FindInPage:Find", s.toString());
     }
@@ -180,43 +185,33 @@ public class FindInPageBar extends Linea
             return;
         }
 
         if (viewId == R.id.find_close) {
             hide();
         }
     }
 
-    // GeckoEventListener implementation
-
-    @Override
-    public void handleMessage(String event, JSONObject message) {
-        if (event.equals("FindInPage:MatchesCountResult")) {
-            onMatchesCountResult(message.optInt("total", 0),
-                message.optInt("current", 0),
-                message.optInt("limit", 0),
-                message.optString("searchString"));
+    @Override // BundleEventListener
+    public void handleMessage(final String event, final GeckoBundle message,
+                              final EventCallback callback) {
+        if ("FindInPage:MatchesCountResult".equals(event)) {
+            onMatchesCountResult(message.getInt("total", 0),
+                message.getInt("current", 0),
+                message.getInt("limit", 0),
+                message.getString("searchString"));
             return;
         }
+    }
 
-        if (!event.equals("TextSelection:Data") || !REQUEST_ID.equals(message.optString("requestId"))) {
-            return;
-        }
-
-        final String text = message.optString("text");
-
+    /* package */ void onTextSelectionData(final String text) {
         // Populate an initial find string, virtual keyboard not required.
         if (!TextUtils.isEmpty(text)) {
             // Populate initial selection
-            ThreadUtils.postToUiThread(new Runnable() {
-                @Override
-                public void run() {
-                    mFindText.setText(text);
-                }
-            });
+            mFindText.setText(text);
             return;
         }
 
         // Show the virtual keyboard.
         if (mFindText.hasWindowFocus()) {
             getInputMethodManager(mFindText).showSoftInput(mFindText, 0);
         } else {
             // showSoftInput won't work until after the window is focused.
@@ -232,25 +227,13 @@ public class FindInPageBar extends Linea
             });
         }
     }
 
     /**
      * Request find operation, and update matchCount results (current count and total).
      */
     private void sendRequestToFinderHelper(final String request, final String searchString) {
-        GeckoAppShell.sendRequestToGecko(new GeckoRequest(request, searchString) {
-            @Override
-            public void onResponse(NativeJSObject nativeJSObject) {
-                // We don't care about the return value, because `onMatchesCountResult`
-                // does the heavy lifting.
-            }
-
-            @Override
-            public void onError(NativeJSObject error) {
-                // Gecko didn't respond due to state change, javascript error, etc.
-                Log.d(LOGTAG, "No response from Gecko on request to match string: [" +
-                    searchString + "]");
-                updateResult("");
-            }
-        });
+        final GeckoBundle data = new GeckoBundle(1);
+        data.putString("searchString", searchString);
+        EventDispatcher.getInstance().dispatch(request, data);
     }
 }

--- a/mobile/android/chrome/content/FindHelper.js
+++ b/mobile/android/chrome/content/FindHelper.js
@@ -7,49 +7,63 @@ var FindHelper = {
   _finder: null,
   _targetTab: null,
   _initialViewport: null,
   _viewportChanged: false,
   _result: null,
 
   // Start of nsIObserver implementation.
 
-  observe: function(aMessage, aTopic, aData) {
-    switch(aTopic) {
+  onEvent: function(event, data, callback) {
+    switch (event) {
       case "FindInPage:Opened": {
         this._findOpened();
         break;
       }
 
-      case "FindInPage:Closed":
+      case "FindInPage:Closed": {
         this._uninit();
         this._findClosed();
         break;
-    }
-  },
+      }
 
-  onEvent: function(event, message, callback) {
-    switch (event) {
       case "Tab:Selected": {
         // Allow for page switching.
         this._uninit();
         break;
       }
+
+      case "FindInPage:Find": {
+        this.doFind(data.searchString);
+        break;
+      }
+
+      case "FindInPage:Next": {
+        this.findAgain(data.searchString, false);
+        break;
+      }
+
+      case "FindInPage:Prev": {
+        this.findAgain(data.searchString, true);
+        break;
+      }
     }
   },
 
   /**
    * When the FindInPageBar opens/ becomes visible, it's time to:
    * 1. Add listeners for other message types sent from the FindInPageBar
    * 2. initialize the Finder instance, if necessary.
    */
   _findOpened: function() {
-    Messaging.addListener(data => this.doFind(data), "FindInPage:Find");
-    Messaging.addListener(data => this.findAgain(data, false), "FindInPage:Next");
-    Messaging.addListener(data => this.findAgain(data, true), "FindInPage:Prev");
+    GlobalEventDispatcher.registerListener(this, [
+      "FindInPage:Find",
+      "FindInPage:Next",
+      "FindInPage:Prev",
+    ]);
 
     // Initialize the finder component for the current page by performing a fake find.
     this._init();
     this._finder.requestMatchesCount("");
   },
 
   /**
    * Fetch the Finder instance from the active tabs' browser and start tracking
@@ -99,19 +113,21 @@ var FindHelper = {
       "Tab:Selected",
     ]);
   },
 
   /**
    * When the FindInPageBar closes, it's time to stop listening for its messages.
    */
   _findClosed: function() {
-    Messaging.removeListener("FindInPage:Find");
-    Messaging.removeListener("FindInPage:Next");
-    Messaging.removeListener("FindInPage:Prev");
+    GlobalEventDispatcher.unregisterListener(this, [
+      "FindInPage:Find",
+      "FindInPage:Next",
+      "FindInPage:Prev",
+    ]);
   },
 
   /**
    * Start an asynchronous find-in-page operation, using the current Finder
    * instance and request to count the amount of matches.
    * If no Finder instance is currently active, we'll lazily initialize it here.
    *
    * @param  {String} searchString Word to search for in the current document
@@ -157,17 +173,17 @@ var FindHelper = {
    *                        the following properties:
    *                        - {Number} total   The total amount of matches found
    *                        - {Number} current The index of current found range
    *                                           in the document
    */
   onMatchesCountResult: function(result) {
     this._result = result;
 
-    Messaging.sendRequest(Object.assign({
+    GlobalEventDispatcher.sendRequest(Object.assign({
       type: "FindInPage:MatchesCountResult"
     }, this._result));
   },
 
   /**
    * When a find-in-page action finishes, this method is invoked. This is mainly
    * used at the moment to detect if the current viewport has changed, which might
    * be indicated by not finding a string in the current page.

--- a/mobile/android/chrome/content/browser.js
+++ b/mobile/android/chrome/content/browser.js
@@ -150,17 +150,16 @@ lazilyLoadedBrowserScripts.forEach(funct
     Services.scriptloader.loadSubScript(script, sandbox);
     return sandbox[name];
   });
 });
 
 var lazilyLoadedObserverScripts = [
   ["MemoryObserver", ["memory-pressure", "Memory:Dump"], "chrome://browser/content/MemoryObserver.js"],
   ["ConsoleAPI", ["console-api-log-event"], "chrome://browser/content/ConsoleAPI.js"],
-  ["FindHelper", ["FindInPage:Opened", "FindInPage:Closed"], "chrome://browser/content/FindHelper.js"],
   ["PermissionsHelper", ["Permissions:Check", "Permissions:Get", "Permissions:Clear"], "chrome://browser/content/PermissionsHelper.js"],
   ["FeedHandler", ["Feeds:Subscribe"], "chrome://browser/content/FeedHandler.js"],
   ["Feedback", ["Feedback:Show"], "chrome://browser/content/Feedback.js"],
   ["EmbedRT", ["GeckoView:ImportScript"], "chrome://browser/content/EmbedRT.js"],
   ["Reader", ["Reader:AddToCache", "Reader:RemoveFromCache"], "chrome://browser/content/Reader.js"],
   ["PrintHelper", ["Print:PDF"], "chrome://browser/content/PrintHelper.js"],
 ];
 
@@ -249,16 +248,19 @@ lazilyLoadedObserverScripts.forEach(func
   });
 });
 
 // Lazily-loaded JS subscripts that use global/window EventDispatcher.
 [
   ["ActionBarHandler", WindowEventDispatcher,
    ["TextSelection:Get", "TextSelection:Action", "TextSelection:End"],
    "chrome://browser/content/ActionBarHandler.js"],
+  ["FindHelper", GlobalEventDispatcher,
+   ["FindInPage:Opened", "FindInPage:Closed"],
+   "chrome://browser/content/FindHelper.js"],
 ].forEach(module => {
   let [name, dispatcher, events, script] = module;
   XPCOMUtils.defineLazyGetter(window, name, function() {
     let sandbox = {};
     Services.scriptloader.loadSubScript(script, sandbox);
     return sandbox[name];
   });
   let listener = (event, message, callback) => {