[HTML Imports] Implement "load" and "error" events.

Source/core/html/LinkImport.h

 /*
  * 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 13 matching lines @@
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef LinkImport_h
 #define LinkImport_h
 
+#include "core/html/HTMLImportLoaderClient.h"
 #include "core/html/LinkResource.h"
 #include "wtf/FastAllocBase.h"
 #include "wtf/RefPtr.h"
 
 namespace WebCore {
 
 class Document;
 class HTMLImportLoader;
 
 //
 // A LinkResource subclasss used for @rel=import.
 //
-class LinkImport : public LinkResource {
+class LinkImport : public LinkResource, public HTMLImportLoaderClient {
     WTF_MAKE_FAST_ALLOCATED;
 public:
 
     static PassRefPtr<LinkImport> create(HTMLLinkElement* owner);
 
     explicit LinkImport(HTMLLinkElement* owner);
     virtual ~LinkImport();
 
     // LinkResource
     virtual void process() OVERRIDE;
     virtual Type type() const OVERRIDE { return Import; }
     virtual void ownerRemoved() OVERRIDE;
+    virtual bool hasLoaded() const OVERRIDE;
+
+    // HTMLImportLoaderClient
+    virtual void didFinish() OVERRIDE;
 
     Document* importedDocument() const;
 
 private:
+    void clear();
+
     RefPtr<HTMLImportLoader> m_loader;
 };
 
 } // namespace WebCore
 
 #endif // LinkImport_h