Revert "Remove legacy check on null NavigationItem in CRWWKNavigationHandler"

This reverts commit 4c3e1c10.

Reason for revert: This CL introduces massive crashes in M78.

Original change's description:
> Remove legacy check on null NavigationItem in CRWWKNavigationHandler
> 
> Now that pending NavigationItem are stored in NavigationContext, it
> will never be null. Remove the legacy code that checks if pending
> NavigationItem exists in CRWWKNavigationHandler.
> 
> Bug: 925304
> Change-Id: I5eb541f068b4a6db1f5322fed2e7318d686a845a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730424
> Commit-Queue: Yi Su <mrsuyi@chromium.org>
> Reviewed-by: Eugene But <eugenebut@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#683507}

TBR=eugenebut@chromium.org,mrsuyi@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 925304
Change-Id: I091ae74a41d23454ac1af0ba6c752af9a6d7f41c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1878749Reviewed-by: Yi Su <mrsuyi@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Yi Su <mrsuyi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709080}

ios/web/navigation/crw_wk_navigation_handler.mm

@@ -805,7 +805,35 @@ void ReportOutOfSyncURLInDidStartProvisionalNavigation(
   // |context| will be nil if this navigation has been already committed and
   // finished.
   if (context) {
+    web::NavigationManager* navigationManager =
+        self.webStateImpl->GetNavigationManager();
+    GURL pendingURL;
+    if (navigationManager->GetPendingItemIndex() == -1) {
+      if (context->GetItem()) {
+        // Item may not exist if navigation was stopped (see
+        // crbug.com/969915).
+        pendingURL = context->GetItem()->GetURL();
+      }
+    } else {
+      if (navigationManager->GetPendingItem()) {
+        pendingURL = navigationManager->GetPendingItem()->GetURL();
+      }
+    }
+    if ((pendingURL == webViewURL) || (context->IsLoadingHtmlString()) ||
+        (!web::GetWebClient()->IsSlimNavigationManagerEnabled() &&
+         ui::PageTransitionCoreTypeIs(context->GetPageTransition(),
+                                      ui::PAGE_TRANSITION_RELOAD) &&
+         navigationManager->GetLastCommittedItem())) {
+      // Commit navigation if at least one of these is true:
+      //  - Navigation has pending item (this should always be true, but
+      //    pending item may not exist due to crbug.com/925304).
+      //  - Navigation is loadHTMLString:baseURL: navigation, which does not
+      //    create a pending item, but modifies committed item instead.
+      //  - Transition type is reload with Legacy Navigation Manager (Legacy
+      //    Navigation Manager does not create pending item for reload due to
+      //    crbug.com/676129)
       context->SetHasCommitted(true);
+    }
     self.webStateImpl->SetContentsMimeType(
         base::SysNSStringToUTF8(context->GetMimeType()));
   }
@@ -2178,6 +2206,12 @@ void ReportOutOfSyncURLInDidStartProvisionalNavigation(
 
 // Updates the WKBackForwardListItemHolder navigation item.
 - (void)updateCurrentBackForwardListItemHolderInWebView:(WKWebView*)webView {
+  if (!self.currentNavItem) {
+    // TODO(crbug.com/925304): Pending item (which stores the holder) should be
+    // owned by NavigationContext object. Pending item should never be null.
+    return;
+  }
+
   web::WKBackForwardListItemHolder* holder =
       self.currentBackForwardListItemHolder;
 
@@ -2319,7 +2353,9 @@ void ReportOutOfSyncURLInDidStartProvisionalNavigation(
   // be extracted from the landing page.)
   web::NavigationItem* currentItem = self.currentNavItem;
 
-  if (!currentItem->GetReferrer().url.is_valid()) {
+  // TODO(crbug.com/925304): Pending item (which should be used here) should be
+  // owned by NavigationContext object. Pending item should never be null.
+  if (currentItem && !currentItem->GetReferrer().url.is_valid()) {
     currentItem->SetReferrer(referrer);
   }
 

ios/web/web_state/web_state_observer_inttest.mm

@@ -316,7 +316,7 @@ ACTION_P5(VerifyDataFinishedContext,
       PageTransitionCoreTypeIs(ui::PageTransition::PAGE_TRANSITION_TYPED,
                                (*context)->GetPageTransition()));
   EXPECT_FALSE((*context)->IsSameDocument());
-  EXPECT_TRUE((*context)->HasCommitted());
+  EXPECT_FALSE((*context)->HasCommitted());
   EXPECT_FALSE((*context)->IsDownload());
   EXPECT_FALSE((*context)->IsPost());
   EXPECT_FALSE((*context)->GetError());