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

Source/core/html/LinkImport.h

Index: Source/core/html/LinkImport.h
diff --git a/Source/core/html/LinkImport.h b/Source/core/html/LinkImport.h
index 57a6a412360923fc8242c9ab9609601bcb65e75e..4003f88525e0553eb48c0bec0c8c073eb50e84bd 100644
--- a/Source/core/html/LinkImport.h
+++ b/Source/core/html/LinkImport.h
@@ -31,6 +31,7 @@
 #ifndef LinkImport_h
 #define LinkImport_h
 
+#include "core/html/HTMLImportLoaderClient.h"
 #include "core/html/LinkResource.h"
 #include "wtf/FastAllocBase.h"
 #include "wtf/RefPtr.h"
@@ -43,7 +44,7 @@ class HTMLImportLoader;
 //
 // A LinkResource subclasss used for @rel=import.
 //
-class LinkImport : public LinkResource {
+class LinkImport : public LinkResource, public HTMLImportLoaderClient {
     WTF_MAKE_FAST_ALLOCATED;
 public:
 
@@ -56,10 +57,16 @@ public:
     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;
 };