[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 bb577bd7c867f043cab396bb6f57e7bc12e7435f..db06acaf5bb0a0bcc85080c7932480e90bcd83a1 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;
 }