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

Source/WebCore/platform/network/ResourceError.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2013 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 15 matching lines @@
 
 #ifndef ResourceError_h
 #define ResourceError_h
 
 #include <wtf/text/WTFString.h>
 
 namespace WebCore {
 
 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;

[darin (slow to review), 2013/04/16 20:25:39]

nit: this is a bit of a layering violation.  platform/network/ shouldn't know
about FrameLoaderClient details.

[Nate Chapin, 2013/04/16 20:40:43]

I'm wondering if we actually need to differentiate between cancellation errors
and policy change errors. It's only used in
FrameLoaderClientImpl::dispatchDidFailProvisionalLoad, where it references a
pre-release chromium bug.

+
 class ResourceError {
 public:
+    static ResourceError createCancelledError(const String& failingURL);

[darin (slow to review), 2013/04/16 20:25:39]

nit: create* methods usually return a heap allocated something.

Also, perhaps these should just live under WebCore/loader/ since they are only
needed at that level?  I was also going to suggest moving them out to the
WebCore namespace:

  ResourceError cancelled{Resource}Error(const String& failingURL);
  ResourceError policyChange{Resource}Error(const String& failingURL);

I could also see the case for subclassing:

  class Cancelled{Resource}Error : public ResourceError { ... };
  class PolicyChange{Resource}Error : public ResourceError { ... };

+    static ResourceError createPolicyChangeError(const String& failingURL);
+
     ResourceError()
         : m_errorCode(0)
         , m_isNull(true)
         , m_isCancellation(false)
         , m_isTimeout(false)
     {
     }
 
     ResourceError(const String& domain, int errorCode, const String& failingURL, const String& localizedDescription)
         : m_domain(domain)
@@ skipping 33 matching lines @@
     bool m_isCancellation;
     bool m_isTimeout;
 };
 
 inline bool operator==(const ResourceError& a, const ResourceError& b) { return ResourceError::compare(a, b); }
 inline bool operator!=(const ResourceError& a, const ResourceError& b) { return !(a == b); }
 
 } // namespace WebCore
 
 #endif // ResourceError_h