[NotLanded] Implement the fetching algorithm of the Web Manifest.

public/web/WebLocalFrame.h

Index: public/web/WebLocalFrame.h
diff --git a/public/web/WebLocalFrame.h b/public/web/WebLocalFrame.h
index ce7cafdbb64c0a8b0dade2b951f97337358975f2..6d6999b1ecec63b91dd8b62c56e4843c9601fae4 100644
--- a/public/web/WebLocalFrame.h
+++ b/public/web/WebLocalFrame.h
@@ -37,6 +37,14 @@ public:
     virtual void navigateToSandboxedMarkup(const WebData& markup) = 0;
 
     virtual void sendPings(const WebNode& linkNode, const WebURL& destinationURL) = 0;
+
+    // Manifest ------------------------------------------------------------
+
+    // Called to fetch and parse a frame's manifest. The associated
+    // WebFrameClient will be notified upon completion via
+    // WebFrameClient::didLoadManifest or WebFrameClient::didFailLoadManifest
+    // depending on the call being successful or not.
+    virtual void requestManifest() = 0;
 };
 
 } // namespace blink