Add link preload as=document support

third_party/WebKit/public/platform/WebURLRequest.h

Index: third_party/WebKit/public/platform/WebURLRequest.h
diff --git a/third_party/WebKit/public/platform/WebURLRequest.h b/third_party/WebKit/public/platform/WebURLRequest.h
index 45a8a860cf1ce7ca402fe7813b21e10f1109396c..5ed0d34d5982bf538d570639f497d717a8a3b404 100644
--- a/third_party/WebKit/public/platform/WebURLRequest.h
+++ b/third_party/WebKit/public/platform/WebURLRequest.h
@@ -101,7 +101,8 @@ public:
         FrameTypeAuxiliary,
         FrameTypeNested,
         FrameTypeNone,
-        FrameTypeTopLevel
+        FrameTypeTopLevel,
+        FrameTypePreload
     };
 
     enum FetchRequestMode {
@@ -281,6 +282,9 @@ public:
     BLINK_PLATFORM_EXPORT LoFiState getLoFiState() const;
     BLINK_PLATFORM_EXPORT void setLoFiState(LoFiState);
 
+    // Is the request triggered by a link preload?
+    BLINK_PLATFORM_EXPORT bool linkPreload() const;
+
     // Extra data associated with the underlying resource request. Resource
     // requests can be copied. If non-null, each copy of a resource requests
     // holds a pointer to the extra data, and the extra data pointer will be