<webview>: Move back, forward, canGoBack, canGoForward, go from content to chrome

chrome/common/extensions/api/webview.json

 // Copyright (c) 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": "webview",
     "nodoc": true,
     "functions": [
       {
@@ skipping 52 matching lines @@
               {
                 "name": "result",
                 "optional": true,
                 "type": "array",
                 "items": {"type": "any", "minimum": 0},
                 "description": "The result of the script in every injected frame."
               }
             ]
           }
         ]
+      },
+      {
+        "name": "go",
+        "type": "function",
+        "parameters": [
+          {
+            "type": "integer",
+            "name": "instanceId"
+          },
+          {
+            "type": "integer",
+            "name": "relativeIndex"
+          }
+        ]
       }
     ]
   }
 ]