Fire accessibilityPrivate events on two-finger hold gesture.

chrome/common/extensions/api/accessibility_private.json

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [
   {
     "namespace": "accessibilityPrivate",
     "compiler_options": {
       "implemented_in": "chrome/browser/accessibility/accessibility_extension_api.h"
     },
@@ skipping 100 matching lines @@
       {
         "name": "onAccessibilityGesture",
         "type": "function",
         "description": "Fired when an accessibility gesture is detected by the touch exploration controller.",
         "parameters": [
           {
             "name": "gesture",
             "$ref": "Gesture"
           }
         ]
+      },
+      {
+        "name": "onTwoFingerTouchStart",
+        "type": "function",
+        "description": "Fired when we first detect two fingers are held down, which can be used to toggle spoken feedback on some touch-only devices.",
+        "parameters": []
+      },
+      {
+        "name": "onTwoFingerTouchStop",
+        "type": "function",
+        "description": "Fired when  the user is no longer holding down two fingers (including releasing one, holding down three, or moving them).",
+        "parameters": []
       }
     ]
   }
 ]