Adds support for POST request with bodies on WKWebView.

ios/web/web_state/js/resources/post_request.js

Index: ios/web/web_state/js/resources/post_request.js
diff --git a/ios/web/web_state/js/resources/post_request.js b/ios/web/web_state/js/resources/post_request.js
new file mode 100644
index 0000000000000000000000000000000000000000..5d13a50c2586c499601650279ce4c1d78a0dc17d
--- /dev/null
+++ b/ios/web/web_state/js/resources/post_request.js
@@ -0,0 +1,78 @@
+// 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');

[Eugene But (OOO till 7-30), 2015/10/08 17:46:32]

s/__crPOSTRequestHack/__crWeb.postRequestHack

[stkhapugin, 2015/12/03 15:43:01]

Done.

+
+/**
+ * Namespace for this file.
+ */
+__crPOSTRequestHack = {};

[Eugene But (OOO till 7-30), 2015/10/08 17:46:32]

__crPostRequestHack

According to JS Style Guide acronyms should use camelCase.
Just search for "Url" here:
https://engdoc.corp.google.com/eng/doc/javascriptguide.xml?cl=head#Naming to
find examples

[stkhapugin, 2015/12/03 15:43:01]

Done.

+
+/**
+ * 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} base64Data Request body encoded with Base64.
+ * @param {string} contentType Content-Type header value.
+ */
+__crPOSTRequestHack.runPOSTRequest = function(url, headers, base64Data,

[Eugene But (OOO till 7-30), 2015/10/08 17:46:32]

NIT: s/base64Data/body this way we can keep consistent terminology

[stkhapugin, 2015/12/03 15:43:01]

Done.

+  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){
+        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});
+      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} b64Data Request body encoded with Base64.
+    * @param {string} contentType Content-Type header value.
+    */
+    var createAndSendPOSTRequest = function(url, headers, b64Data, contentType){

[Eugene But (OOO till 7-30), 2015/10/08 17:46:32]

createAndSendPostRequest

[Eugene But (OOO till 7-30), 2015/10/08 17:46:32]

NIT: s/b64Data/body

[stkhapugin, 2015/12/03 15:43:01]

Done.

[stkhapugin, 2015/12/03 15:43:01]

Done.

+      var request = new XMLHttpRequest();
+      request.open('POST', url, false);
+      for (var key in headers) {
+        request.setRequestHeader(key, headers[key]);

[Eugene But (OOO till 7-30), 2015/10/08 17:46:32]

You want to make hasOwnProperty check, otherwise your |key| may come from
|headers| superclass.

[stkhapugin, 2015/12/03 15:43:01]

Done.

+      }
+      var blob = base64ToBlob(atob(b64Data), contentType);
+      request.send(blob);
+      if (request.status != 200) {
+        throw request.status;

[stuartmorgan, 2015/10/08 19:11:29]

Why are we throwing a JS exception for non-200 status?

More generally, what exactly does happen if, e.g., a user tries to re-post and
there's an error.

[stkhapugin, 2015/12/03 15:43:01]

I added an error handler that catches any non-200 HTTP status and sends it over
to Objective-C code via message handlers. Then the standard logic for displaying
errors is executed in CRWWKWebViewWebController. The only question I have is how
to wrap this into an NSError cleanly, i.e. which error domain I should use and
is there any userInfo that should be provided (localized description etc)? 

+      }
+      return request.responseText;
+    }
+
+    document.open();
+    document.write(createAndSendPOSTRequest(url, headers, base64Data,

[Eugene But (OOO till 7-30), 2015/10/08 17:46:32]

document.write reinjects our scripts w/o giving us any callbacks (sorry I missed
this during the last codereview).
Could you please check if Find In Page works after Search By Image.

[stkhapugin, 2015/12/03 15:43:01]

Done.

+      contentType));
+      document.close();
+    }