Create errors (especially cancellation errors) internally to WebCore, rather

Source/core/platform/network/ResourceError.cpp

Index: Source/core/platform/network/ResourceError.cpp
===================================================================
--- Source/core/platform/network/ResourceError.cpp	(revision 148828)
+++ Source/core/platform/network/ResourceError.cpp	(working copy)
@@ -27,10 +27,20 @@
 #include "config.h"
 #include "ResourceError.h"
 
+#include <public/Platform.h>
+
 namespace WebCore {
 
 const char* const errorDomainWebKitInternal = "WebKitInternal";
 
+ResourceError ResourceError::cancelledError(const String& failingURL)
+{
+    ResourceError error(WebKit::Platform::current()->cancelledErrorDomain(),
+        WebKit::Platform::current()->cancelledErrorCode(), failingURL, String());
+    error.setIsCancellation(true);
+    return error;
+}
+
 ResourceError ResourceError::copy() const
 {
     ResourceError errorCopy;