<webview>: Remove broken captureVisibleRegion code until feature is properly supported

extensions/common/api/web_view_internal.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": "webViewInternal",
     "description": "none",
     "compiler_options": {
       "implemented_in": "extensions/browser/api/web_view/web_view_internal_api.h"
@@ skipping 110 matching lines @@
           {
             "type": "function",
             "name": "callback",
             "optional": true,
             "description": "Called when all the CSS has been inserted.",
             "parameters": []
           }
         ]
       },
       {
-        "name": "captureVisibleRegion",
-        "type": "function",
-        "description": "Captures the visible area of the currently loaded page inside <webview>.",
-        "parameters": [
-          {
-            "type": "integer",
-            "name": "instanceId",
-            "description": "The instance ID of the guest <webview> process."
-          },
-          {
-            "$ref": "extensionTypes.ImageDetails",
-            "name": "options",
-            "optional": true
-          },
-          {
-            "type": "function", "name": "callback", "parameters": [
-              {"type": "string", "name": "dataUrl", "description": "A data URL which encodes an image of the visible area of the captured tab. May be assigned to the 'src' property of an HTML Image element for display."}
-            ]
-          }
-        ]
-      },
-      {
         "name": "setZoom",
         "type": "function",
         "parameters": [
           {
             "type": "integer",
             "name": "instanceId",
             "description": "The instance ID of the guest <webview> process."
           },
           {
             "type": "number",
@@ skipping 335 matching lines @@
             "type": "function",
             "description": "Called when deletion has completed.",
             "optional": true,
             "parameters": []
           }
         ]
       }
     ]
   }
 ]