Remove isolated app code from iOS's chrome_browser_state_io_data.

ios/chrome/browser/browser_state/chrome_browser_state.h

Index: ios/chrome/browser/browser_state/chrome_browser_state.h
diff --git a/ios/chrome/browser/browser_state/chrome_browser_state.h b/ios/chrome/browser/browser_state/chrome_browser_state.h
index 31548b912ce1939f09463a194119e870c5ad5f93..afbce100df609f340606496c18c3c333eb63c59f 100644
--- a/ios/chrome/browser/browser_state/chrome_browser_state.h
+++ b/ios/chrome/browser/browser_state/chrome_browser_state.h
@@ -126,11 +126,6 @@ class ChromeBrowserState : public web::BrowserState {
           protocol_handlers,
       ScopedVector<net::URLRequestInterceptor> request_interceptors) = 0;
 
-  // Creates a isolated net::URLRequestContextGetter. Should only be called once
-  // per partition_path per browser state object.
-  virtual net::URLRequestContextGetter* CreateIsolatedRequestContext(
-      const base::FilePath& partition_path) = 0;
-
   // Returns the current ChromeBrowserState casted as a TestChromeBrowserState
   // or null if it is not a TestChromeBrowserState.
   // TODO(crbug.com/583682): This method should not be used. It is there for