[ios] Added web// public API to let embedder observe loading progress.

ios/web/public/test/test_web_state.mm

Index: ios/web/public/test/test_web_state.mm
diff --git a/ios/web/public/test/test_web_state.mm b/ios/web/public/test/test_web_state.mm
index ebd739e0f8c272cf7c40da621466551ecbc5866a..a659af8d7c1b22d0639bc5a0ed8070e9e9c42648 100644
--- a/ios/web/public/test/test_web_state.mm
+++ b/ios/web/public/test/test_web_state.mm
@@ -17,6 +17,12 @@ UIView* TestWebState::GetView() {
   return nullptr;
 }
 
+WebStateDelegate* TestWebState::GetDelegate() {
+  return nil;
+}
+
+void TestWebState::SetDelegate(WebStateDelegate* delegate) {}
+
 BrowserState* TestWebState::GetBrowserState() const {
   return nullptr;
 }