[ios] Do not use private web// API in ios_web_shell.

ios/web/public/web_state/web_state.h

Index: ios/web/public/web_state/web_state.h
diff --git a/ios/web/public/web_state/web_state.h b/ios/web/public/web_state/web_state.h
index d9dfe653e0a1beeb14bf928a6acf244a663a26b6..c8f310927adbaf94c75767293dc74f58a5c74d6c 100644
--- a/ios/web/public/web_state/web_state.h
+++ b/ios/web/public/web_state/web_state.h
@@ -48,6 +48,14 @@ class WebStateWeakPtrFactory;
 // Core interface for interaction with the web.
 class WebState : public base::SupportsUserData {
  public:
+  // Parameters for the Create() method.
+  struct CreateParams {
+    explicit CreateParams(web::BrowserState* browser_state);
+    ~CreateParams();
+
+    web::BrowserState* browser_state;
+  };
+
   // Parameters for the OpenURL() method.
   struct OpenURLParams {
     OpenURLParams(const GURL& url,
@@ -84,6 +92,9 @@ class WebState : public base::SupportsUserData {
       const std::vector<gfx::Size>&)>
           ImageDownloadCallback;
 
+  // Creates a new WebState.
+  static std::unique_ptr<WebState> Create(const CreateParams& params);
+
   ~WebState() override {}
 
   // Gets/Sets the delegate.