Revert to the old back arrow style with NavigationBar

ios/chrome/browser/ui/settings/settings_navigation_controller.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.
 
 #import "ios/chrome/browser/ui/settings/settings_navigation_controller.h"
 
 #include "base/ios/ios_util.h"
 #import "base/ios/weak_nsobject.h"
 #include "base/mac/foundation_util.h"
 #import "base/mac/scoped_nsobject.h"
@@ skipping 60 matching lines @@
 @end
 
 @interface SettingsNavigationController ()<UIGestureRecognizerDelegate>
 
 // Sets up the UI.  Used by both initializers.
 - (void)configureUI;
 
 // Closes the settings by calling |closeSettings| on |delegate|.
 - (void)closeSettings;
 
+// Creates an autoreleased Back button for a UINavigationItem which will pop the
+// top view controller when it is pressed. Should only be called by view
+// controllers owned by SettingsNavigationController.
+- (UIBarButtonItem*)backButton;
+
 // Creates an autoreleased "X" button that closes the settings when tapped.
 - (UIBarButtonItem*)closeButton;
 
 // Creates an autoreleased "CANCEL" button that closes the settings when tapped.
 - (UIBarButtonItem*)cancelButton;
 
 // Intercepts the chrome command |sender|. If |sender| is an
 // |IDC_CLOSE_SETTINGS_AND_OPEN_URL| and |delegate_| is not nil, then it
 // calls [delegate closeSettingsAndOpenUrl:sender], otherwise it forwards the
 // command up the responder chain.
@@ skipping 221 matching lines @@
 
   // Reset the delegate to prevent any queued transitions from attempting to
   // close the settings.
   delegate_.reset();
 }
 
 - (void)closeSettings {
   [delegate_ closeSettings];
 }
 
+- (void)back {
+  [self popViewControllerAnimated:YES];
+}
+
 - (void)popViewControllerOrCloseSettingsAnimated:(BOOL)animated {
   if (self.viewControllers.count > 1) {
     // Pop the top view controller to reveal the view controller underneath.
     [self popViewControllerAnimated:animated];
   } else {
     // If there is only one view controller in the navigation stack,
     // simply close settings.
     [self closeSettings];
   }
 }
@@ skipping 12 matching lines @@
 - (BOOL)hasRightDoneButton {
   UIBarButtonItem* rightButton =
       self.topViewController.navigationItem.rightBarButtonItem;
   if (!rightButton)
     return NO;
   base::scoped_nsobject<UIBarButtonItem> doneButton([self doneButton]);
   return [rightButton style] == [doneButton style] &&
          [[rightButton title] compare:[doneButton title]] == NSOrderedSame;
 }
 
+- (UIBarButtonItem*)backButton {
+  // Create a custom Back bar button item, as Material Navigation Bar deprecated
+  // the back arrow with a shaft.
+  return [ChromeIcon templateBarButtonItemWithImage:[ChromeIcon backIcon]
+                                             target:self
+                                             action:@selector(back)];
+}
+
 - (UIBarButtonItem*)doneButton {
   // Create a custom Done bar button item, as Material Navigation Bar does not
   // handle a system UIBarButtonSystemItemDone item.
   return [[[UIBarButtonItem alloc]
       initWithTitle:l10n_util::GetNSString(IDS_IOS_NAVIGATION_BAR_DONE_BUTTON)
               style:UIBarButtonItemStyleDone
              target:self
              action:@selector(closeSettings)] autorelease];
 }
 
@@ skipping 37 matching lines @@
   UIViewController* poppedController = [self popViewControllerAnimated:YES];
   if (!poppedController)
     [self closeSettings];
   return YES;
 }
 
 #pragma mark - UINavigationController
 
 - (void)pushViewController:(UIViewController*)viewController
                   animated:(BOOL)animated {
+  // Add a back button if the view controller is not the root view controller
+  // and doesn’t already have a left bar button item.
+  if (self.viewControllers.count > 0 &&
+      viewController.navigationItem.leftBarButtonItems.count == 0) {
+    viewController.navigationItem.leftBarButtonItem = [self backButton];
+  }
   // Wrap the view controller in an MDCAppBarContainerViewController if needed.
   [super pushViewController:[self wrappedControllerIfNeeded:viewController]
                    animated:animated];
 }
 
 - (UIViewController*)popViewControllerAnimated:(BOOL)animated {
   UIViewController* viewController = [super popViewControllerAnimated:animated];
   // Unwrap the view controller from its MDCAppBarContainerViewController if
   // needed.
   return [self unwrappedControllerIfNeeded:viewController];
@@ skipping 206 matching lines @@
   NSValue* key = [self keyForController:controller];
   return [appBarContainedViewControllers_ objectForKey:key];
 }
 
 // Returns the dictionary key to use when dealing with |controller|.
 - (NSValue*)keyForController:(UIViewController*)controller {
   return [NSValue valueWithPointer:controller];
 }
 
 @end