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

Source/WebCore/platform/network/ResourceError.h

Index: Source/WebCore/platform/network/ResourceError.h
===================================================================
--- Source/WebCore/platform/network/ResourceError.h	(revision 148290)
+++ Source/WebCore/platform/network/ResourceError.h	(working copy)
@@ -33,8 +33,15 @@
 
 extern const char* const errorDomainWebKitInternal; // Used for errors that won't be exposed to clients.
 
+// An internal error code.  Used to note a policy change error resulting from
+// dispatchDecidePolicyForMIMEType not passing the PolicyUse option.
+extern const int policyChangeError;
+
 class ResourceError {
 public:
+    static ResourceError createCancelledError(const String& failingURL);
+    static ResourceError createPolicyChangeError(const String& failingURL);
+
     ResourceError()
         : m_errorCode(0)
         , m_isNull(true)