Remove Javascript POST workaround when running on iOS 11 or later

BUG=581021

Change-Id: Id6d7ab0cabc525cd575f6140281fdf5dc213a2b9
Reviewed-on: https://chromium-review.googlesource.com/565786Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#485460}

ios/web/web_state/ui/crw_web_controller.mm

@@ -5057,16 +5057,21 @@ registerLoadRequestForURL:(const GURL&)requestURL
     [request setHTTPMethod:@"POST"];
     [request setHTTPBody:POSTData];
     [request setAllHTTPHeaderFields:self.currentHTTPHeaders];
-    GURL navigationURL =
-        currentItem ? currentItem->GetURL() : GURL::EmptyGURL();
-    std::unique_ptr<web::NavigationContextImpl> navigationContext =
-        [self registerLoadRequestForURL:navigationURL
-                               referrer:self.currentNavItemReferrer
-                             transition:self.currentTransition];
-    WKNavigation* navigation = [self loadPOSTRequest:request];
-    [_navigationStates setContext:std::move(navigationContext)
-                    forNavigation:navigation];
-    return;
+    // As of iOS 11, WKWebView supports requests with POST data, so the
+    // Javascript POST workaround only needs to be used if the OS version is
+    // less than iOS 11.
+    if (!base::ios::IsRunningOnIOS11OrLater()) {
+      GURL navigationURL =
+          currentItem ? currentItem->GetURL() : GURL::EmptyGURL();
+      std::unique_ptr<web::NavigationContextImpl> navigationContext =
+          [self registerLoadRequestForURL:navigationURL
+                                 referrer:self.currentNavItemReferrer
+                               transition:self.currentTransition];
+      WKNavigation* navigation = [self loadPOSTRequest:request];
+      [_navigationStates setContext:std::move(navigationContext)
+                      forNavigation:navigation];
+      return;
+    }
   }
 
   ProceduralBlock defaultNavigationBlock = ^{