[ios] Retry injection of windowID if it has failed.

ios/web/web_state/ui/crw_web_controller.mm

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/web/web_state/ui/crw_web_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #import <objc/runtime.h>
 #include <stddef.h>
@@ skipping 2505 matching lines @@
 - (BOOL)scriptHasBeenInjectedForClass:(Class)JSInjectionManagerClass
                        presenceBeacon:(NSString*)beacon {
   return [_injectedScriptManagers containsObject:JSInjectionManagerClass];
 }
 
 - (void)injectScript:(NSString*)script forClass:(Class)JSInjectionManagerClass {
   // Skip evaluation if there's no content (e.g., if what's being injected is
   // an umbrella manager).
   if ([script length]) {
     // Every injection except windowID requires windowID check.
-    if (JSInjectionManagerClass != [CRWJSWindowIdManager class])
+    if (JSInjectionManagerClass != [CRWJSWindowIdManager class]) {
       script = [self scriptByAddingWindowIDCheckForScript:script];
-    web::ExecuteJavaScript(_webView, script, nil);
+      web::ExecuteJavaScript(_webView, script, nil);
+    } else {
+      web::ExecuteJavaScript(_webView, script, ^(id, NSError* error) {
+        // TODO(crbug.com/628832): Refactor retry logic.
+        if (error.code == WKErrorJavaScriptExceptionOccurred) {
+          // This can happen if WKUserScript has not been injected yet.

[kkhorimoto, 2016/07/18 18:29:36]

There are other reasons why we can get an exception right?  If this is failing
for a different reason, wouldn't this cause an infinite loop of injection
attempts?

[Eugene But (OOO till 7-30), 2016/07/18 18:43:09]

The other reason is a bug inside window_id.js, but in this case a bunch of our
integration tests will fail and we will fix the script. So I think than infinite
loop will not happen in practice. Do you want me to explicitly document this in
the comments?

+          // Retry if that's the case, because windowID injection is critical
+          // for the system to function.
+          [_injectedScriptManagers removeObject:JSInjectionManagerClass];
+          [self injectWindowID];
+        }
+      });
+    }
   }
   [_injectedScriptManagers addObject:JSInjectionManagerClass];
 }
 
 #pragma mark -
 
 - (void)evaluateUserJavaScript:(NSString*)script {
   [self setUserInteractionRegistered:YES];
   web::ExecuteJavaScript(_webView, script, nil);
 }
@@ skipping 3123 matching lines @@
   }
 
   return web::WEB_VIEW_DOCUMENT_TYPE_GENERIC;
 }
 
 - (NSString*)refererFromNavigationAction:(WKNavigationAction*)action {
   return [action.request valueForHTTPHeaderField:@"Referer"];
 }
 
 @end