Implement Blink-side changes to enable V8 code caching.

Source/core/fetch/Resource.h

Index: Source/core/fetch/Resource.h
diff --git a/Source/core/fetch/Resource.h b/Source/core/fetch/Resource.h
index 1fbd46baa26a43718e8ed8dcf001c431c179854b..481cf6588e1e1da674308662dbae4a3bf4c3e240 100644
--- a/Source/core/fetch/Resource.h
+++ b/Source/core/fetch/Resource.h
@@ -196,6 +196,9 @@ public:
     // identifier that is used to distinguish data generated by the caller.
     void setCachedMetadata(unsigned dataTypeID, const char*, size_t);
 
+    // Reset existing metadata, to allow setting new data.
+    void clearCachedMetadata();
+
     // Returns cached metadata of the given type associated with this resource.
     CachedMetadata* cachedMetadata(unsigned dataTypeID) const;