Refactor the API for setting dynamic resource load priorities

Source/core/fetch/ResourceClient.h

Index: Source/core/fetch/ResourceClient.h
diff --git a/Source/core/fetch/ResourceClient.h b/Source/core/fetch/ResourceClient.h
index ef337982907f6f35fe5ddc996e01d18bba7632de..3bb76f42137123e803230bf7368298aa18516751 100644
--- a/Source/core/fetch/ResourceClient.h
+++ b/Source/core/fetch/ResourceClient.h
@@ -26,6 +26,7 @@
 #define ResourceClient_h
 
 #include "core/CoreExport.h"
+#include "platform/network/ResourceLoadPriority.h"
 #include "wtf/FastAllocBase.h"
 #include "wtf/Forward.h"
 
@@ -50,6 +51,8 @@ public:
     static ResourceClientType expectedType() { return BaseResourceType; }
     virtual ResourceClientType resourceClientType() const { return expectedType(); }
 
+    virtual ResourcePriority updatePriority(Resource*) { return ResourcePriority(); }
+
 protected:
     ResourceClient() { }
 };