Plumb manifest fetching through WebTestDelegate interface

content/shell/renderer/layout_test/blink_test_runner.h

Index: content/shell/renderer/layout_test/blink_test_runner.h
diff --git a/content/shell/renderer/layout_test/blink_test_runner.h b/content/shell/renderer/layout_test/blink_test_runner.h
index c0e7dc9598ecbb3d171f5fd82351d886d3475d0e..9b7b2c6ecd3a68519575fdefae8e4b5378c365bb 100644
--- a/content/shell/renderer/layout_test/blink_test_runner.h
+++ b/content/shell/renderer/layout_test/blink_test_runner.h
@@ -109,6 +109,11 @@ class BlinkTestRunner : public RenderViewObserver,
                        const std::string& frame_name) override;
   bool AllowExternalPages() override;
   std::string DumpHistoryForWindow(WebTestProxyBase* proxy) override;
+  void FetchManifest(
+      blink::WebView* view,
+      const GURL& url,
+      const base::Callback<void(const blink::WebURLResponse& response,
+                                const std::string& data)>& callback) override;
   void SetPermission(const std::string& name,
                      const std::string& value,
                      const GURL& origin,