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

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index 847c3a69eda9aae9ed46f97cf7d3793afc5ef224..b48615c6ee3d71fa2b7f31a2bcfbf267bd16a05b 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -2523,9 +2523,21 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
   // 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];
 }