Move the notion of current Tab from TabModel to WebStateList.

ios/chrome/browser/tabs/tab.mm

 // Copyright 2012 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/chrome/browser/tabs/tab.h"
 
 #import <CoreLocation/CoreLocation.h>
 #import <UIKit/UIKit.h>
 
 #include <utility>
@@ skipping 724 matching lines @@
 }
 
 - (CRWWebController*)webController {
   return webStateImpl_ ? webStateImpl_->GetWebController() : nil;
 }
 
 - (id<TabDialogDelegate>)dialogDelegate {
   return dialogDelegate_;
 }
 
+- (BOOL)loadFinished {
+  return [self.webController loadPhase] == web::PAGE_LOADED;
+}
+
 - (void)setDialogDelegate:(id<TabDialogDelegate>)dialogDelegate {
   dialogDelegate_.reset(dialogDelegate);
 }
 
 - (void)setIsVoiceSearchResultsTab:(BOOL)isVoiceSearchResultsTab {
   // There is intentionally no equality check in this setter, as we want the
   // notificaiton to be sent regardless of whether the value has changed.
   isVoiceSearchResultsTab_ = isVoiceSearchResultsTab;
   [parentTabModel_ notifyTabChanged:self];
 }
@@ skipping 1492 matching lines @@
 
 - (TabModel*)parentTabModel {
   return parentTabModel_;
 }
 
 - (FormInputAccessoryViewController*)inputAccessoryViewController {
   return inputAccessoryViewController_.get();
 }
 
 @end