Improve xhr/setrequestheader-content-type.htm result

Improve xhr/setrequestheader-content-type.htm result by doing two fixes:
- Apply Content-Type processing steps for Documents, just like for Strings [1].
- Apply Content-Type processing steps also for empty Content-Type value [2].

This matches Firefox and WebKit.

[1] https://xhr.spec.whatwg.org/#the-send()-method 4.4.1
[2] https://xhr.spec.whatwg.org/#the-send()-method 4.4

Bug: 626703

Change-Id: Ie09df6e711b04a30b6181914f3b59bb8cf4e6a49
Reviewed-on: https://chromium-review.googlesource.com/1189602Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Rob Buis <rbuis@igalia.com>
Cr-Commit-Position: refs/heads/master@{#587059}

third_party/WebKit/LayoutTests/external/wpt/xhr/send-content-type-charset-expected.txt

 This is a testharness.js-based test.
 FAIL header with invalid MIME type is not changed assert_equals: expected "text; charset=ascii" but got "text; charset=UTF-8"
-FAIL header with invalid MIME type (empty string) is not changed assert_equals: expected "" but got "text/plain;charset=UTF-8"
+PASS header with invalid MIME type (empty string) is not changed
 PASS known charset but bogus header - missing MIME type
 PASS bogus charset and bogus header - missing MIME type
 PASS Correct text/plain MIME with charset

third_party/WebKit/LayoutTests/external/wpt/xhr/setrequestheader-content-type-expected.txt

 This is a testharness.js-based test.
-FAIL setRequestHeader("") sends a blank string assert_equals: expected "Content-Type: \n" but got "Content-Type: , text/plain;charset=UTF-8\n"
-FAIL setRequestHeader(" ") sends the string " " assert_equals: expected "Content-Type: \n" but got "Content-Type: , text/plain;charset=UTF-8\n"
+PASS setRequestHeader("") sends a blank string
+PASS setRequestHeader(" ") sends the string " "
 PASS setRequestHeader(null) sends the string "null"
 PASS setRequestHeader(undefined) sends the string "undefined"
 PASS String request has correct default Content-Type of "text/plain;charset=UTF-8"
 PASS String request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8
 PASS XML Document request respects setRequestHeader("")
 PASS XML Document request has correct default Content-Type of "application/xml;charset=UTF-8"
-FAIL XML Document request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8 assert_equals: expected "Content-Type: application/xhtml+xml;charset=UTF-8\n" but got "Content-Type: application/xhtml+xml;charset=ASCII\n"
+PASS XML Document request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8
 PASS HTML Document request respects setRequestHeader("")
-FAIL HTML Document request has correct default Content-Type of "text/html;charset=UTF-8" assert_equals: expected "Content-Type: text/html;charset=UTF-8\n" but got "Content-Type: application/xml;charset=UTF-8\n"
-FAIL HTML Document request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8 assert_equals: expected "Content-Type: text/html+junk;charset=UTF-8\n" but got "Content-Type: text/html+junk;charset=ASCII\n"
+PASS HTML Document request has correct default Content-Type of "text/html;charset=UTF-8"
+PASS HTML Document request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8
 PASS Blob request respects setRequestHeader("") to be specified
 PASS Blob request with unset type sends no Content-Type without setRequestHeader() call
 PASS Blob request with unset type keeps setRequestHeader() Content-Type and charset
@@ -26,10 +26,10 @@ PASS ArrayBufferView request keeps setRequestHeader() Content-Type and charset
 PASS FormData request respects setRequestHeader("")
 PASS FormData request has correct default Content-Type of "multipart/form-data; boundary=_"
 PASS FormData request keeps setRequestHeader() Content-Type and charset
-FAIL URLSearchParams respects setRequestHeader("") assert_equals: expected "Content-Type: \n" but got "Content-Type: , application/x-www-form-urlencoded;charset=UTF-8\n"
+PASS URLSearchParams respects setRequestHeader("")
 PASS URLSearchParams request has correct default Content-Type of "application/x-www-form-urlencoded;charset=UTF-8"
 PASS URLSearchParams request keeps setRequestHeader() Content-Type, with charset adjusted to UTF-8
-FAIL ReadableStream request respects setRequestHeader("") assert_equals: expected "Content-Type: \n" but got "Content-Type: , text/plain;charset=UTF-8\n"
+PASS ReadableStream request respects setRequestHeader("")
 FAIL ReadableStream request with under type sends no Content-Type without setRequestHeader() call assert_equals: expected "" but got "Content-Type: text/plain;charset=UTF-8\n"
 FAIL ReadableStream request keeps setRequestHeader() Content-Type and charset assert_equals: expected "Content-Type: application/xml;charset=ASCII\n" but got "Content-Type: application/xml;charset=UTF-8\n"
 Harness: the test ran to completion.

third_party/WebKit/LayoutTests/http/tests/xmlhttprequest/send-document-content-type-charset.html

@@ -14,7 +14,7 @@ async_test(function(t) {
   xhr.open("POST", "print-content-type.cgi");
   xhr.send(document);
   xhr.onloadend = t.step_func_done(function() {
-    assert_equals(xhr.responseText, "application/xml;charset=UTF-8\n");
+    assert_equals(xhr.responseText, "text/html;charset=UTF-8\n");
   });
 });
 </script>

third_party/blink/renderer/core/xmlhttprequest/xml_http_request.cc

@@ -827,12 +827,10 @@ void XMLHttpRequest::send(Document* document, ExceptionState& exception_state) {
   scoped_refptr<EncodedFormData> http_body;
 
   if (AreMethodAndURLValidForSend()) {
-    // FIXME: Per https://xhr.spec.whatwg.org/#dom-xmlhttprequest-send the
-    // Content-Type header and whether to serialize as HTML or XML should
-    // depend on |document->isHTMLDocument()|.
-    if (!HasContentTypeRequestHeader())
-      SetRequestHeaderInternal(HTTPNames::Content_Type,
-                               "application/xml;charset=UTF-8");
+    if (document->IsHTMLDocument())
+      UpdateContentTypeAndCharset("text/html;charset=UTF-8", "UTF-8");
+    else if (document->IsXMLDocument())
+      UpdateContentTypeAndCharset("application/xml;charset=UTF-8", "UTF-8");
 
     String body = CreateMarkup(document);
 
@@ -1542,7 +1540,7 @@ void XMLHttpRequest::UpdateContentTypeAndCharset(
   // http://xhr.spec.whatwg.org/#the-send()-method step 4's concilliation of
   // "charset=" in any author-provided Content-Type: request header.
   String content_type = request_headers_.Get(HTTPNames::Content_Type);
-  if (content_type.IsEmpty()) {
+  if (content_type.IsNull()) {
     SetRequestHeaderInternal(HTTPNames::Content_Type, default_content_type);
     return;
   }