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 148396)
+++ 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;

[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)