Add a runtime flag in WebRuntimeFeatures to enable 'image/webp' accept header

Source/WebKit/chromium/public/WebRuntimeFeatures.h

Index: Source/WebKit/chromium/public/WebRuntimeFeatures.h
diff --git a/Source/WebKit/chromium/public/WebRuntimeFeatures.h b/Source/WebKit/chromium/public/WebRuntimeFeatures.h
index 51213d21bb67be81a40b422ad502ad0b0bdae89e..6a073e0effc9ffea8b7040873e7a9d097c4c71bb 100644
--- a/Source/WebKit/chromium/public/WebRuntimeFeatures.h
+++ b/Source/WebKit/chromium/public/WebRuntimeFeatures.h
@@ -170,6 +170,10 @@ public:
     // instead of the embedder.
     WEBKIT_EXPORT static void enableDoNotTrack(bool);
     WEBKIT_EXPORT static bool isDoNotTrackEnabled();
+
+    WEBKIT_EXPORT static void enableWebPInAcceptHeader(bool);
+    WEBKIT_EXPORT static bool isWebPInAcceptHeaderEnabled();
+
 private:
     WebRuntimeFeatures();
 };