Adds test coverage for 521663

Source/web/tests/FrameTestHelpers.h

Index: Source/web/tests/FrameTestHelpers.h
diff --git a/Source/web/tests/FrameTestHelpers.h b/Source/web/tests/FrameTestHelpers.h
index 6800cf78faca681a30bbc927e60d5c98ff977b4e..dcc4066591c82902bc73ce509280c9d0c7bf61c6 100644
--- a/Source/web/tests/FrameTestHelpers.h
+++ b/Source/web/tests/FrameTestHelpers.h
@@ -162,6 +162,18 @@ public:
     }
 };
 
+// Task that calls loadRequest() when run().
+class LoadTask : public WebThread::Task {
+public:
+    LoadTask(WebFrame*, const WebURLRequest&);
+
+    void run() override;
+
+private:
+    WebFrame* const m_frame;
+    const WebURLRequest m_request;
+};
+
 } // namespace FrameTestHelpers
 } // namespace blink