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

ios/chrome/browser/metrics/tab_usage_recorder.mm

 // Copyright 2013 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.
 
 #include "ios/chrome/browser/metrics/tab_usage_recorder.h"
 
 #include "base/metrics/histogram_macros.h"
 #include "ios/chrome/browser/chrome_url_constants.h"
 #import "ios/chrome/browser/metrics/previous_session_info.h"
 #import "ios/chrome/browser/tabs/tab.h"
+#import "ios/web/public/navigation_item.h"
+#import "ios/web/public/navigation_manager.h"
+#import "ios/web/public/web_state/web_state.h"
 #import "ios/web/web_state/ui/crw_web_controller.h"
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 const char kTabUsageHistogramPrefix[] = "Tab";
 
 // The histogram recording the state of the tab the user switches to.
 const char kSelectedTabHistogramName[] =
@@ skipping 270 matching lines @@
 
 void TabUsageRecorder::ResetEvictedTab() {
   evicted_tab_ = NULL;
   evicted_tab_state_ = IN_MEMORY;
   evicted_tab_reload_start_time_ = base::TimeTicks();
 }
 
 bool TabUsageRecorder::ShouldIgnoreTab(Tab* tab) {
   // Do not count chrome:// urls to avoid data noise.  For example, if they were
   // counted, every new tab created would add noise to the page load count.
-  return [tab url].SchemeIs(kChromeUIScheme);
+  web::NavigationItem* pending_item =
+      tab.webState->GetNavigationManager()->GetPendingItem();
+  if (pending_item)
+    return pending_item->GetURL().SchemeIs(kChromeUIScheme);
+  return tab.lastCommittedURL.SchemeIs(kChromeUIScheme);
 }
 
 bool TabUsageRecorder::TabAlreadyEvicted(Tab* tab) {
   base::WeakNSObject<Tab> weak_tab(tab);
   auto tab_item = evicted_tabs_.find(weak_tab);
   return tab_item != evicted_tabs_.end();
 }
 
 TabUsageRecorder::TabStateWhenSelected TabUsageRecorder::ExtractTabState(
     Tab* tab) {
@@ skipping 19 matching lines @@
 }
 
 void TabUsageRecorder::ClearDeletedTabs() {
   base::WeakNSObject<Tab> empty_tab(nil);
   auto tab_item = evicted_tabs_.find(empty_tab);
   while (tab_item != evicted_tabs_.end()) {
     evicted_tabs_.erase(empty_tab);
     tab_item = evicted_tabs_.find(empty_tab);
   }
 }