--- a/b2g/chrome/content/shell.js
+++ b/b2g/chrome/content/shell.js
@@ -319,16 +319,18 @@ var shell = {
     // Capture all key events so we can filter out hardware buttons
     // And send them to Gaia via mozChromeEvents.
     // Ideally, hardware buttons wouldn't generate key events at all, or
     // if they did, they would use keycodes that conform to DOM 3 Events.
     // See discussion in https://bugzilla.mozilla.org/show_bug.cgi?id=762362
     chromeEventHandler.addEventListener('keydown', this, true);
     chromeEventHandler.addEventListener('keypress', this, true);
     chromeEventHandler.addEventListener('keyup', this, true);
+    chromeEventHandler.addEventListener('mozbrowserbeforekeydown', this, true);
+    chromeEventHandler.addEventListener('mozbrowserbeforekeyup', this, true);
 
     window.addEventListener('MozApplicationManifest', this);
     window.addEventListener('mozfullscreenchange', this);
     window.addEventListener('MozAfterPaint', this);
     window.addEventListener('sizemodechange', this);
     window.addEventListener('unload', this);
     this.contentBrowser.addEventListener('mozbrowserloadstart', this, true);
     this.contentBrowser.addEventListener('mozbrowserselectionchange', this, true);
@@ -351,16 +353,18 @@ var shell = {
     ppmm.addMessageListener("file-picker", this);
   },
 
   stop: function shell_stop() {
     window.removeEventListener('unload', this);
     window.removeEventListener('keydown', this, true);
     window.removeEventListener('keypress', this, true);
     window.removeEventListener('keyup', this, true);
+    window.removeEventListener('mozbrowserbeforekeydown', this, true);
+    window.removeEventListener('mozbrowserbeforekeyup', this, true);
     window.removeEventListener('MozApplicationManifest', this);
     window.removeEventListener('mozfullscreenchange', this);
     window.removeEventListener('sizemodechange', this);
     this.contentBrowser.removeEventListener('mozbrowserloadstart', this, true);
     this.contentBrowser.removeEventListener('mozbrowserselectionchange', this, true);
     this.contentBrowser.removeEventListener('mozbrowserscrollviewchange', this, true);
     this.contentBrowser.removeEventListener('mozbrowsertouchcarettap', this, true);
     ppmm.removeMessageListener("content-handler", this);
@@ -415,27 +419,24 @@ var shell = {
       isMediaKey = true;
       type = mediaKeys[evt.key];
     }
 
     if (!type) {
       return;
     }
 
-    // If we didn't return, then the key event represents a hardware key
-    // and we need to prevent it from propagating to Gaia
-    evt.stopImmediatePropagation();
-    evt.preventDefault(); // Prevent keypress events (when #501496 is fixed).
-
     // If it is a key down or key up event, we send a chrome event to Gaia.
     // If it is a keypress event we just ignore it.
     switch (evt.type) {
+      case 'mozbrowserbeforekeydown':
       case 'keydown':
         type = type + '-press';
         break;
+      case 'mozbrowserbeforekeyup':
       case 'keyup':
         type = type + '-release';
         break;
       case 'keypress':
         return;
     }
 
     // Let applications receive the headset button key press/release event.
@@ -468,16 +469,18 @@ var shell = {
   visibleNormalAudioActive: false,
 
   handleEvent: function shell_handleEvent(evt) {
     let content = this.contentBrowser.contentWindow;
     switch (evt.type) {
       case 'keydown':
       case 'keyup':
       case 'keypress':
+      case 'mozbrowserbeforekeydown':
+      case 'mozbrowserbeforekeyup':
         this.filterHardwareKeys(evt);
         break;
       case 'mozfullscreenchange':
         // When the screen goes fullscreen make sure to set the focus to the
         // main window so noboby can prevent the ESC key to get out fullscreen
         // mode
         if (document.mozFullScreen)
           Services.fm.focusedWindow = window;

--- a/dom/apps/PermissionsTable.jsm
+++ b/dom/apps/PermissionsTable.jsm
@@ -488,16 +488,22 @@ this.PermissionsTable =  { geolocation: 
                              access: ["read", "write"],
                              additional: ["settings-api"]
                            },
                            "engineering-mode": {
                              app: DENY_ACTION,
                              trusted: DENY_ACTION,
                              privileged: DENY_ACTION,
                              certified: ALLOW_ACTION
+                           },
+                           "before-after-keyboard-event": {
+                             app: DENY_ACTION,
+                             trusted: DENY_ACTION,
+                             privileged: DENY_ACTION,
+                             certified: ALLOW_ACTION
                            }
                          };
 
 /**
  * Append access modes to the permission name as suffixes.
  *   e.g. permission name 'contacts' with ['read', 'write'] =
  *   ['contacts-read', contacts-write']
  * @param string aPermName

--- a/testing/mochitest/manifest.webapp
+++ b/testing/mochitest/manifest.webapp
@@ -22,17 +22,18 @@
     "camera":{},
     "geolocation":{},
     "wifi-manage":{},
     "desktop-notification":{},
     "idle":{},
     "network-events":{},
     "embed-apps":{},
     "audio-channel-content":{},
-    "audio-channel-alarm":{}
+    "audio-channel-alarm":{},
+    "before-after-keyboard-event":{}
   },
   "locales": {
     "en-US": {
       "name": "Mochitest",
       "description": "Mochitests"
     }
   },
   "datastores-access" : {