Deprecate support for xhr.withCredentials for synchronous requests

Source/core/xml/XMLHttpRequest.cpp

Index: Source/core/xml/XMLHttpRequest.cpp
diff --git a/Source/core/xml/XMLHttpRequest.cpp b/Source/core/xml/XMLHttpRequest.cpp
index 3befd8e2073a228de6f5b8b423db4ba35ff31784..7aa0ed04895aabab1b67416981b673b5a5f2e53d 100644
--- a/Source/core/xml/XMLHttpRequest.cpp
+++ b/Source/core/xml/XMLHttpRequest.cpp
@@ -36,6 +36,8 @@
 #include "core/fileapi/Blob.h"
 #include "core/fileapi/File.h"
 #include "core/fileapi/Stream.h"
+#include "core/frame/Settings.h"
+#include "core/frame/UseCounter.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "core/html/DOMFormData.h"
 #include "core/html/HTMLDocument.h"
@@ -43,7 +45,6 @@
 #include "core/inspector/InspectorInstrumentation.h"
 #include "core/inspector/InspectorTraceEvents.h"
 #include "core/loader/ThreadableLoader.h"
-#include "core/frame/Settings.h"
 #include "core/xml/XMLHttpRequestProgressEvent.h"
 #include "core/xml/XMLHttpRequestUpload.h"
 #include "platform/Logging.h"
@@ -486,6 +487,13 @@ void XMLHttpRequest::setWithCredentials(bool value, ExceptionState& exceptionSta
         return;
     }
 
+    // FIXME: According to XMLHttpRequest Level 2 we should throw InvalidAccessError exception here.
+    // However for time being only throw warning message to console for web developers.
+    if (!m_async && executionContext()->isDocument()) {
+        UseCounter::countDeprecation(document(), UseCounter::SyncXHRWithCredentials);
+        return;

[sof, 2014/06/16 14:21:34]

If I understand your intent correctly, isn't this doing something a bit
stronger? i.e., it's issuing a deprecation message and ignoring the value being
set.

[Inactive, 2014/06/16 17:07:32]

sof@ is right, IMHO. We should probably not ignore the input value until we get
usage numbers. It is too early to do this IMO, we should just add a usecounter
(and print the deprecation warning if API Owners are OK with it).

+    }
+
     m_includeCredentials = value;
 }