Implement webview.captureVisibleRegion()

extensions/renderer/resources/guest_view/web_view/web_view_experimental.js

+// Copyright 2015 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.
+
+// This module implements experimental API for <webview>.
+// See web_view.js and web_view_api_methods.js for details.
+//
+// <webview> Experimental API is only available on canary and channels of
+// Chrome.
+
+var WebViewImpl = require('webView').WebViewImpl;
+var WebViewInternal = require('webViewInternal').WebViewInternal;
+
+// An array of <webview>'s experimental API methods.  See |WEB_VIEW_API_METHODS|
+// in web_view_api_methods.js for more details.
+var WEB_VIEW_EXPERIMENTAL_API_METHODS = [
+  // Captures the visible region of the WebView contents into a bitmap.
+  'captureVisibleRegion'
+];
+
+// Registers the experimantal WebVIew API when available.
+WebViewImpl.maybeGetExperimentalApiMethods = function() {
+  return WEB_VIEW_EXPERIMENTAL_API_METHODS;
+};