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

public/web/WebFrameClient.h

Index: public/web/WebFrameClient.h
diff --git a/public/web/WebFrameClient.h b/public/web/WebFrameClient.h
index ff19656543895482adacd59ac393e9a90383450a..29e7aaeb0db1e14484bf492cfa4cfe922882db65 100644
--- a/public/web/WebFrameClient.h
+++ b/public/web/WebFrameClient.h
@@ -46,6 +46,7 @@
 #include "public/platform/WebCommon.h"
 #include "public/platform/WebFileSystem.h"
 #include "public/platform/WebFileSystemType.h"
+#include "public/platform/WebManifestError.h" // can't fwd declare enum.
 #include "public/platform/WebStorageQuotaCallbacks.h"
 #include "public/platform/WebStorageQuotaType.h"
 #include "public/platform/WebURLError.h"
@@ -92,6 +93,7 @@ class WebWorkerPermissionClientProxy;
 struct WebColorSuggestion;
 struct WebConsoleMessage;
 struct WebContextMenuData;
+struct WebManifest;
 struct WebPluginParams;
 struct WebPopupMenuInfo;
 struct WebRect;
@@ -299,11 +301,20 @@ public:
     // WARNING: This method may be called very frequently.
     virtual void didUpdateCurrentHistoryItem(WebLocalFrame*) { }
 
+    // The frame's theme color has changed.
+    virtual void didChangeThemeColor() { }
+
+
+    // Web Manifest ---------------------------------------------------------
+
     // The frame's manifest has changed.
     virtual void didChangeManifest(WebLocalFrame*) { }
 
-    // The frame's theme color has changed.
-    virtual void didChangeThemeColor() { }
+    // The frame's manifest has been loaded successfully.
+    virtual void didLoadManifest(WebLocalFrame*, const WebManifest&) { }
+
+    // The frame's manifest loading has failed.
+    virtual void didFailLoadManifest(WebLocalFrame*, WebManifestError) { }
 
 
     // Transition navigations -----------------------------------------------