Ignore title changes from WKWebView when the web process dies

ios/web/web_state/ui/crw_wk_web_view_web_controller.mm

 // Copyright 2014 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_wk_web_view_web_controller.h"
 
 #import <WebKit/WebKit.h>
 
 #include "base/containers/mru_cache.h"
 #include "base/ios/ios_util.h"
@@ skipping 194 matching lines @@
   // CertVerification errors which happened inside
   // |webView:didReceiveAuthenticationChallenge:completionHandler:|.
   // Key is leaf-cert/host pair. This storage is used to carry calculated
   // cert status from |didReceiveAuthenticationChallenge:| to
   // |didFailProvisionalNavigation:| delegate method.
   scoped_ptr<CertVerificationErrorsCacheType> _certVerificationErrors;
 
   // YES if the user has interacted with the content area since the last URL
   // change.
   BOOL _interactionRegisteredSinceLastURLChange;
+
+  // YES if the web process backing _wkWebView is believed to currently be dead.
+  BOOL _webProcessIsDead;
 }
 
 // Dictionary where keys are the names of WKWebView properties and values are
 // selector names which should be called when a corresponding property has
 // changed. e.g. @{ @"URL" : @"webViewURLDidChange" } means that
 // -[self webViewURLDidChange] must be called every time when WKWebView.URL is
 // changed.
 @property(nonatomic, readonly) NSDictionary* wkWebViewObservers;
 
 // Activity indicator group ID for this web controller.
@@ skipping 655 matching lines @@
 
   base::WeakNSObject<CRWWKWebViewWebController> weakSelf(self);
   id crashHandler = ^{
     [weakSelf webViewWebProcessDidCrash];
   };
   return [[CRWWKWebViewCrashDetector alloc] initWithWebView:webView
                                                crashHandler:crashHandler];
 }
 
 - (void)webViewWebProcessDidCrash {
+  _webProcessIsDead = YES;
   if ([self.delegate respondsToSelector:
           @selector(webControllerWebProcessDidCrash:)]) {
     [self.delegate webControllerWebProcessDidCrash:self];
   }
 }
 
 - (void)queryPageReferrerPolicy:(void(^)(NSString*))responseHandler {
   DCHECK(responseHandler);
   [self evaluateJavaScript:@"__gCrWeb.getPageReferrerPolicy()"
        stringResultHandler:^(NSString* referrer, NSError* error) {
@@ skipping 571 matching lines @@
 
 - (void)webViewLoadingStateDidChange {
   if ([_wkWebView isLoading]) {
     [self addActivityIndicatorTask];
   } else {
     [self clearActivityIndicatorTasks];
   }
 }
 
 - (void)webViewTitleDidChange {
+  // WKWebView's title becomes empty when the web process dies; ignore that
+  // update.
+  if (_webProcessIsDead) {
+    DCHECK_EQ(self.title.length, 0U);
+    return;
+  }
+
   if ([self.delegate respondsToSelector:
           @selector(webController:titleDidChange:)]) {
     DCHECK(self.title);
     [self.delegate webController:self titleDidChange:self.title];
   }
 }
 
 - (void)webViewURLDidChange {
   // TODO(stuartmorgan): Determine if there are any cases where this still
   // happens, and if so whether anything should be done when it does.
@@ skipping 52 matching lines @@
   }
 }
 
 #pragma mark -
 #pragma mark WKNavigationDelegate Methods
 
 - (void)webView:(WKWebView *)webView
     decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction
                     decisionHandler:
         (void (^)(WKNavigationActionPolicy))decisionHandler {
+  _webProcessIsDead = NO;
   if (self.isBeingDestroyed) {
     decisionHandler(WKNavigationActionPolicyCancel);
     return;
   }
 
   NSURLRequest* request = navigationAction.request;
   GURL url = net::GURLWithNSURL(request.URL);
 
   // The page will not be changed until this navigation is commited, so the
   // retrieved state will be pending until |didCommitNavigation| callback.
@@ skipping 288 matching lines @@
         runJavaScriptTextInputPanelWithPrompt:prompt
                                   defaultText:defaultText
                                    requestURL:requestURL
                             completionHandler:completionHandler];
   } else if (completionHandler) {
     completionHandler(nil);
   }
 }
 
 @end