Add a --enable-gesture-typing flag. Currently this flag does nothing.

extensions/common/api/virtual_keyboard_private.json

 // Copyright 2013 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": "virtualKeyboardPrivate",
     "compiler_options": {
       "implemented_in": "extensions/browser/api/virtual_keyboard_private/virtual_keyboard_private_api.h"
     },
@@ skipping 125 matching lines @@
                     "minLength": 1,
                     "description": "Virtual keyboard layout string."
                   },
                   "a11ymode": {
                     "type": "boolean",
                     "description": "True if accessibility virtual keyboard is enabled."
                   },
                   "experimental": {
                     "type": "boolean",
                     "description": "True if experimental features are enabled."
+                  },
+                  "gesturetyping": {
+                    "type": "boolean",
+                    "description": "True if gesture typing is enabled."
                   }
                 }
               }
             ]
           }
         ]
       },
       {
         "name": "openSettings",
         "type": "function",
@@ skipping 18 matching lines @@
                 "description": "The value of type attribute of the focused text input box.",
                 "enum": ["text", "number", "password", "date", "url", "tel", "email"]
               }
             }
           }
         ]
       }
     ]
   }
 ]