Modernize layout of toolbar items for ios web shell

The manual layout of the toolbar items for ios_web_shell is
outdated and no longer works with iOS 11. Update the UIButtons to
UIBarButtonItems and automatically lay them out with setItems: instead
of adding items as subviews to the UIToolbar.

Bug: None
Change-Id: Id04d7bd7b630c28b0f76f3dc0f78510bca650ffd
Reviewed-on: https://chromium-review.googlesource.com/580148Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Mike Dougherty <michaeldo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#488411}

ios/web/shell/app_delegate.mm

@@ -35,6 +35,7 @@
   _window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
   [self.window makeKeyAndVisible];
   self.window.backgroundColor = [UIColor whiteColor];
+  self.window.tintColor = [UIColor darkGrayColor];
 
   _delegate.reset(new web::ShellMainDelegate());
 

ios/web/shell/view_controller.mm

@@ -84,26 +84,18 @@ using web::NavigationManager;
   [self.view addSubview:_containerView];
 
   // Set up the toolbar buttons.
-  UIButton* back = [UIButton buttonWithType:UIButtonTypeCustom];
-  [back setImage:[UIImage imageNamed:@"toolbar_back"]
-        forState:UIControlStateNormal];
-  [back setFrame:CGRectMake(0, 0, 44, 44)];
-  [back setImageEdgeInsets:UIEdgeInsetsMake(5, 5, 4, 4)];
-  [back setAutoresizingMask:UIViewAutoresizingFlexibleRightMargin];
-  [back addTarget:self
-                action:@selector(back)
-      forControlEvents:UIControlEventTouchUpInside];
+  UIBarButtonItem* back = [[UIBarButtonItem alloc]
+      initWithImage:[UIImage imageNamed:@"toolbar_back"]
+              style:UIBarButtonItemStylePlain
+             target:self
+             action:@selector(back)];
   [back setAccessibilityLabel:kWebShellBackButtonAccessibilityLabel];
 
-  UIButton* forward = [UIButton buttonWithType:UIButtonTypeCustom];
-  [forward setImage:[UIImage imageNamed:@"toolbar_forward"]
-           forState:UIControlStateNormal];
-  [forward setFrame:CGRectMake(44, 0, 44, 44)];
-  [forward setImageEdgeInsets:UIEdgeInsetsMake(5, 5, 4, 4)];
-  [forward setAutoresizingMask:UIViewAutoresizingFlexibleRightMargin];
-  [forward addTarget:self
-                action:@selector(forward)
-      forControlEvents:UIControlEventTouchUpInside];
+  UIBarButtonItem* forward = [[UIBarButtonItem alloc]
+      initWithImage:[UIImage imageNamed:@"toolbar_forward"]
+              style:UIBarButtonItemStylePlain
+             target:self
+             action:@selector(forward)];
   [forward setAccessibilityLabel:kWebShellForwardButtonAccessibilityLabel];
 
   base::scoped_nsobject<UITextField> field([[UITextField alloc]
@@ -120,9 +112,9 @@ using web::NavigationManager;
   [field setClearButtonMode:UITextFieldViewModeWhileEditing];
   self.field = field;
 
-  [_toolbarView addSubview:back];
-  [_toolbarView addSubview:forward];
-  [_toolbarView addSubview:field];
+  [_toolbarView setItems:@[
+    back, forward, [[UIBarButtonItem alloc] initWithCustomView:field]
+  ]];
 
   web::WebState::CreateParams webStateCreateParams(_browserState);
   _webState = web::WebState::Create(webStateCreateParams);