Use correct WebTestDelegate from WebViewTestClient and WebTestProxyBase.

components/test_runner/web_test_proxy.h

Index: components/test_runner/web_test_proxy.h
diff --git a/components/test_runner/web_test_proxy.h b/components/test_runner/web_test_proxy.h
index 14e4952556cd407ba0bd2561fcf49dda27e1bac2..408ac87b73e0abf11ca170fbe9e0664c46d4692d 100644
--- a/components/test_runner/web_test_proxy.h
+++ b/components/test_runner/web_test_proxy.h
@@ -72,8 +72,14 @@ class TEST_RUNNER_EXPORT WebTestProxyBase {
     view_test_client_ = std::move(view_test_client);
   }
 
+  WebTestDelegate* delegate() { return delegate_; }
+  void set_delegate(WebTestDelegate* delegate) {
+    DCHECK(delegate);
+    DCHECK(!delegate_);
+    delegate_ = delegate;
+  }
+
   void SetInterfaces(WebTestInterfaces* interfaces);
-  void SetDelegate(WebTestDelegate* delegate);
 
   std::string DumpBackForwardLists();