Fix the T-Rex easter egg on iOS.

In this CL:
- Always supply a user agent to WKWebViews in web//'s creation methods.
  This allows the IS_IOS variable in offline.js to be correctly set to
  true.
- Delay initializing the game runner until after images have been
  loaded.
- Check for existence of errorPageController when activating the game.

BUG=none

Review-Url: https://codereview.chromium.org/2144933002
Cr-Commit-Position: refs/heads/master@{#406949}

components/neterror/resources/offline.js

@@ -292,7 +292,13 @@ Runner.prototype = {
       this.spriteDef = Runner.spriteDefinition.LDPI;
     }
 
-    this.init();
+    if (Runner.imageSprite.complete) {
+      this.init();
+    } else {
+      // If the images are not yet loaded, add a listener.
+      Runner.imageSprite.addEventListener(Runner.events.LOAD,
+          this.init.bind(this));
+    }
   },
 
   /**
@@ -660,7 +666,9 @@ Runner.prototype = {
         if (!this.activated) {
           this.loadSounds();
           this.activated = true;
-          errorPageController.trackEasterEgg();
+          if (window.errorPageController) {
+            errorPageController.trackEasterEgg();
+          }
         }
 
         if (!this.tRex.jumping && !this.tRex.ducking) {

ios/web/web_state/web_view_internal_creation_util.mm

@@ -33,32 +33,35 @@ WKWebView* CreateWKWebView(CGRect frame,
                            WKWebViewConfiguration* configuration,
                            BrowserState* browser_state,
                            BOOL use_desktop_user_agent) {
-  WKWebView* web_view = CreateWKWebView(frame, configuration, browser_state);
-  web_view.customUserAgent = base::SysUTF8ToNSString(
-      web::GetWebClient()->GetUserAgent(use_desktop_user_agent));
-  return web_view;
-}
-
-WKWebView* CreateWKWebView(CGRect frame,
-                           WKWebViewConfiguration* configuration,
-                           BrowserState* browser_state) {
   VerifyWKWebViewCreationPreConditions(browser_state, configuration);
 
   GetWebClient()->PreWebViewCreation();
-  WKWebView* result =
+  WKWebView* web_view =
       [[WKWebView alloc] initWithFrame:frame configuration:configuration];
 
+  // Set the user agent.
+  web_view.customUserAgent = base::SysUTF8ToNSString(
+      web::GetWebClient()->GetUserAgent(use_desktop_user_agent));
+
   // By default the web view uses a very sluggish scroll speed. Set it to a more
   // reasonable value.
-  result.scrollView.decelerationRate = UIScrollViewDecelerationRateNormal;
+  web_view.scrollView.decelerationRate = UIScrollViewDecelerationRateNormal;
 
   // Starting in iOS10, |allowsLinkPreview| defaults to YES.  This should be
   // disabled since the default implementation will open the link in Safari.
   // TODO(crbug.com/622746): Remove once web// link preview implementation is
   // created.
-  result.allowsLinkPreview = NO;
+  web_view.allowsLinkPreview = NO;
+
+  return web_view;
+}
 
-  return result;
+WKWebView* CreateWKWebView(CGRect frame,
+                           WKWebViewConfiguration* configuration,
+                           BrowserState* browser_state) {
+  BOOL use_desktop_user_agent = NO;
+  return CreateWKWebView(frame, configuration, browser_state,
+                         use_desktop_user_agent);
 }
 
 }  // namespace web