Remove usage of Tab's |url| property from TabModel.

ios/chrome/browser/tabs/tab_model.mm

Index: ios/chrome/browser/tabs/tab_model.mm
diff --git a/ios/chrome/browser/tabs/tab_model.mm b/ios/chrome/browser/tabs/tab_model.mm
index 193dd1f2225c928b458b6e721b8a817aa3b2a4f4..d6b6abb0dd47217e6383256764b3a44cb84cd1b7 100644
--- a/ios/chrome/browser/tabs/tab_model.mm
+++ b/ios/chrome/browser/tabs/tab_model.mm
@@ -593,9 +593,18 @@ - (NSSet*)currentlyReferencedExternalFiles {
     return referencedFiles;
   // Check the currently open tabs for external files.
   for (Tab* tab in self) {
-    if (UrlIsExternalFileReference(tab.url)) {
-      NSString* fileName = base::SysUTF8ToNSString(tab.url.ExtractFileName());
-      [referencedFiles addObject:fileName];
+    const GURL& lastCommittedURL = tab.lastCommittedURL;
+    if (UrlIsExternalFileReference(lastCommittedURL)) {
+      [referencedFiles addObject:base::SysUTF8ToNSString(
+                                     lastCommittedURL.ExtractFileName())];
+    }
+    web::NavigationItem* pendingItem =
+        tab.webState->GetNavigationManager()->GetPendingItem();
+    const GURL& pendingURL =
+        pendingItem ? pendingItem->GetURL() : GURL::EmptyGURL();
+    if (UrlIsExternalFileReference(pendingURL)) {

[Eugene But (OOO till 7-30), 2017/06/01 18:32:09]

nit: How about |if (pendingItem &&
UrlIsExternalFileReference(pendingItem->GetURL()))| ?

[kkhorimoto, 2017/06/01 19:42:29]

Done.

+      [referencedFiles
+          addObject:base::SysUTF8ToNSString(pendingURL.ExtractFileName())];
     }
   }
   // Do the same for the recently closed tabs.
@@ -748,7 +757,9 @@ - (BOOL)restoreSessionWindow:(SessionWindowIOS*)window
   BOOL closedNTPTab = NO;
   if (oldCount == 1) {
     Tab* tab = [self tabAtIndex:0];
-    if (tab.url == GURL(kChromeUINewTabURL)) {
+    BOOL hasPendingLoad =
+        tab.webState->GetNavigationManager()->GetPendingItem() != nullptr;
+    if (!hasPendingLoad && tab.lastCommittedURL == GURL(kChromeUINewTabURL)) {
       [self closeTab:tab];
       closedNTPTab = YES;
       oldCount = 0;