Treat loads of invalid URLs as no-ops unless triggered by window.open.

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 6e5ae32c21d697a687a03e16476677f7c5f03dcd..4f03cc6e35e57d70111e54a120d197d8b89642e7 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -4304,14 +4304,17 @@ - (void)webView:(WKWebView*)webView
   // retrieved state will be pending until |didCommitNavigation| callback.
   [self updatePendingNavigationInfoFromNavigationAction:action];
 
-  // Invalid URLs should not be loaded.  However, simply doing nothing upon
-  // tapping a link or button is a jarring user experience.  Instead, cancel
-  // the invalid navigation and load about:blank if navigation was requested for
-  // the main frame.
+  // Invalid URLs should not be loaded.
   GURL requestURL = net::GURLWithNSURL(action.request.URL);
   if (!requestURL.is_valid()) {
     decisionHandler(WKNavigationActionPolicyCancel);
-    if (action.targetFrame.mainFrame) {
+    // The HTML5 spec indicates that window.open with an invalid URL should open
+    // about:blank.
+    BOOL isFirstLoadInOpenedWindow =
+        self.webState->HasOpener() &&
+        !self.webState->GetNavigationManager()->GetLastCommittedItem();
+    BOOL isMainFrame = action.targetFrame.mainFrame;
+    if (isFirstLoadInOpenedWindow && isMainFrame) {

[Eugene But (OOO till 7-30), 2017/04/06 18:34:19]

I thought this will break CRWWebControllerInvalidUrlTest.LoadInvalidURL, but it
does not. Do you know why?

[kkhorimoto, 2017/04/07 00:03:40]

It looks like WKWebView's |-loadHTMLString:baseURL:| rewrites invalid URLs to
about:blank before reaching this delegate callback.  I've created a bug and
added a TODO to revisit what we want to do with that test.  I'm not sure if we
depend on that behavior for that specific WKWebView API.

[Eugene But (OOO till 7-30), 2017/04/07 01:03:36]

Sorry looks like that test was useless :( I will delete it.

       GURL aboutBlankURL(url::kAboutBlankURL);
       web::NavigationManager::WebLoadParams loadParams(aboutBlankURL);
       loadParams.referrer = [self currentReferrer];