Make touch accessibility gestures work with ChromeVox Next

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 64 matching lines @@
             "description": "True if key events should be swallowed natively and not propagated if preventDefault() gets called by the extension's background page."
           }
         ]
       }
     ],
     "events": [
       {
         "name": "onIntroduceChromeVox",
         "type": "function",
         "description": "Fired whenever ChromeVox should output introduction."
+      },
+      {
+        "name": "onAccessibilityGesture",
+        "type": "function",
+        "description": "Fired when an accessibility gesture is detected by the touch exploration controller.",
+        "parameters": [
+          {
+            "name": "gesture",
+            "type": "string"

[asargent_no_longer_on_chrome, 2016/05/09 19:04:54]

optional suggestion: since the values of this come from an enum in C++, you can
add a "enum" key here mapped to a list of the possible strings, and then you'll
get validity checking from the bindings layer for free (also documentation
nicety, although I guess that doesn't matter for a private API since we don't
generate docs for it). 

[dmazzoni, 2016/05/09 20:03:33]

Done.

+          }
+        ]
       }
     ]
   }
 ]