Remove support for the externalResourcesRequired attribute.

Source/core/svg/SVGDefsElement.h

Index: Source/core/svg/SVGDefsElement.h
diff --git a/Source/core/svg/SVGDefsElement.h b/Source/core/svg/SVGDefsElement.h
index 60ff06beb4aa7a6606beebc1278a1693e0e3667d..72e6f6a46afb7f03083ac3147f56702614826246 100644
--- a/Source/core/svg/SVGDefsElement.h
+++ b/Source/core/svg/SVGDefsElement.h
@@ -22,13 +22,11 @@
 #define SVGDefsElement_h
 
 #include "core/svg/SVGAnimatedBoolean.h"
-#include "core/svg/SVGExternalResourcesRequired.h"
 #include "core/svg/SVGGraphicsElement.h"
 
 namespace WebCore {
 
-class SVGDefsElement FINAL : public SVGGraphicsElement,
-                             public SVGExternalResourcesRequired {
+class SVGDefsElement FINAL : public SVGGraphicsElement {
 public:
     static PassRefPtr<SVGDefsElement> create(Document&);
 
@@ -40,7 +38,6 @@ private:
     virtual RenderObject* createRenderer(RenderStyle*);
 
     BEGIN_DECLARE_ANIMATED_PROPERTIES(SVGDefsElement)
-        DECLARE_ANIMATED_BOOLEAN(ExternalResourcesRequired, externalResourcesRequired)
     END_DECLARE_ANIMATED_PROPERTIES
 };