Adds support for POST request with bodies on WKWebView.

ios/web/web_state/js/resources/post_request.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.
+
+// Provides a way to implement POST requests via XMLHttpRequest.
+// Works around https://bugs.webkit.org/show_bug.cgi?id=145410 on WKWebView.
+
+'use strict';
+
+goog.provide('__crPostRequestHack');
+
+/**
+ * Namespace for this file.
+ */
+__crPostRequestHack = {};
+
+/**
+ * Executes a POST request with given parameters and replaces document body with
+ * the response.
+ * @param {string} url The url of the request.
+ * @param {Object<string,string>} headers Request headers to include in POST.
+ * Each header value must be expressed as a key-value pair in this object.
+ * @param {string} body Request body encoded with Base64.
+ * @param {string} contentType Content-Type header value.
+ */
+__crPostRequestHack.runPostRequest = function(url, headers, body,
+  contentType) {
+
+    /**
+     * Converts a Base64-encoded string to a blob.
+     * @param {string} byteCharacters Base64-encoded data string.
+     * @param {string} contentType Corresponding content type.
+     * @return {Blob} Binary representation of byteCharacters.
+     */
+    var base64ToBlob = function(byteCharacters, contentType) {
+      contentType = contentType || '';
+      var sliceSize = 512;
+      var byteArrays = [];
+      for (var offset = 0; offset < byteCharacters.length; offset += sliceSize){

[Eugene But (OOO till 7-30), 2015/12/02 17:06:16]

Space before |{|, here and everywhere.

[stkhapugin, 2015/12/03 15:43:02]

Done.

+        var slice = byteCharacters.slice(offset, offset + sliceSize);
+        var byteNumbers = new Array(slice.length);
+        for (var i = 0; i < slice.length; i++) {
+          byteNumbers[i] = slice.charCodeAt(i);
+        }
+        var byteArray = new Uint8Array(byteNumbers);
+        byteArrays.push(byteArray);
+      }
+      var blob = new Blob(byteArrays, {type: contentType});

[Eugene But (OOO till 7-30), 2015/12/02 17:06:16]

return new Blob(byteArrays, {type: contentType});

[stkhapugin, 2015/12/03 15:43:02]

Done.

+      return blob;
+    }
+
+    /**
+    * Creates and executes a POST request.
+    * @param {string} url The url of the request.
+    * @param {Object<string,string>} headers Request headers to include in POST.
+    * Each header value must be expressed as a key-value pair in this object.
+    * @param {string} body Request body encoded with Base64.
+    * @param {string} contentType Content-Type header value.
+    */
+    var createAndSendPostRequest = function(url, headers, body, contentType){
+      var request = new XMLHttpRequest();
+      request.open('POST', url, false);
+      for (var key in headers) {
+        if (headers.hasOwnProperty(key)) {
+          request.setRequestHeader(key, headers[key]);
+        }
+      }
+      var blob = base64ToBlob(atob(body), contentType);
+      request.send(blob);
+      if (request.status != 200) {
+        throw request.status;
+      }
+      return request.responseText;
+    }
+
+    document.open();
+    try {
+      document.write(createAndSendPostRequest(url, headers, body,
+      contentType));

[Eugene But (OOO till 7-30), 2015/12/02 17:06:16]

This does not look like correct formatting

[stkhapugin, 2015/12/03 15:43:02]

Done.

+      window.webkit.messageHandlers.POSTSuccess.postMessage("");
+    } catch(error) {
+      window.webkit.messageHandlers.POSTErrorHandler.postMessage(error);
+    }
+      document.close();
+    }