Introduce AsyncDocumentSubresourceFilter.

third_party/WebKit/public/platform/WebDocumentSubresourceFilter.h

Index: third_party/WebKit/public/platform/WebDocumentSubresourceFilter.h
diff --git a/third_party/WebKit/public/platform/WebDocumentSubresourceFilter.h b/third_party/WebKit/public/platform/WebDocumentSubresourceFilter.h
index 8bc2745f32c6b5bcd7dfad8af42a3e9501743d1f..88c6e131b8b3c7a7e4eaeb5e985dfbdb6b0ba171 100644
--- a/third_party/WebKit/public/platform/WebDocumentSubresourceFilter.h
+++ b/third_party/WebKit/public/platform/WebDocumentSubresourceFilter.h
@@ -5,6 +5,7 @@
 #ifndef WebDocumentSubresourceFilter_h
 #define WebDocumentSubresourceFilter_h
 
+#include "public/platform/WebDocumentSubresourceFilterLoadPolicy.h"
 #include "public/platform/WebURLRequest.h"
 
 namespace blink {
@@ -13,10 +14,11 @@ class WebURL;
 
 class WebDocumentSubresourceFilter {
  public:
-  enum LoadPolicy { Allow, Disallow, WouldDisallow };
   virtual ~WebDocumentSubresourceFilter() {}
-  virtual LoadPolicy getLoadPolicy(const WebURL& resourceUrl,
-                                   WebURLRequest::RequestContext) = 0;
+
+  virtual WebDocumentSubresourceFilterLoadPolicy getLoadPolicy(
+      const WebURL& resourceUrl,
+      WebURLRequest::RequestContext) = 0;
 
   // Report that a resource loaded by the document (not a preload) was
   // disallowed.