[iOS] Updates link label to texts view in welcome screen

based on: https://crrev.com/c/2300383
This CL updates the link label used to display the TOS string to an UITextView.
A sublcass is needed to override the |canBecomeFirstResponder| method.

On iOS 13,we can't override |canBecomeFirstResponder| or the whole
string will responds to a tap.

On iOS 12, the whole string responds to a tap if we use this current
implementation.

Bug: 1102996
Change-Id: Id9c9e3089d07a056c365043e1d60b1b558586ccf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2302900
Commit-Queue: Ewann Pellé <ewannpv@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791755}

ios/chrome/browser/ui/elements/BUILD.gn

@@ -18,6 +18,8 @@ source_set("elements") {
     "selector_view_controller_delegate.h",
     "text_field_configuration.h",
     "text_field_configuration.mm",
+    "text_view_selection_disabled.h",
+    "text_view_selection_disabled.mm",
     "top_aligned_image_view.h",
     "top_aligned_image_view.mm",
     "windowed_container_view.h",

ios/chrome/browser/ui/elements/text_view_selection_disabled.h

+// Copyright 2020 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.
+
+#ifndef IOS_CHROME_BROWSER_UI_ELEMENTS_TEXT_VIEW_SELECTION_DISABLED_H_
+#define IOS_CHROME_BROWSER_UI_ELEMENTS_TEXT_VIEW_SELECTION_DISABLED_H_
+
+#import <UIKit/UIKit.h>
+
+// UITextView subclass is needed to override -canBecomeFirstResponder to prevent
+// text selection while maintaining clickable link.
+@interface TextViewSelectionDisabled : UITextView
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_ELEMENTS_TEXT_VIEW_SELECTION_DISABLED_H_

ios/chrome/browser/ui/elements/text_view_selection_disabled.mm

+// Copyright 2020 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/elements/text_view_selection_disabled.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@implementation TextViewSelectionDisabled
+
+- (BOOL)canBecomeFirstResponder {
+  if (@available(iOS 14.0, *))
+    return NO;
+
+  // On iOS 13, the whole string responds to a tap if
+  // canBecomeFirstResponder returns NO.
+  return YES;
+}
+
+@end

ios/chrome/browser/ui/first_run/BUILD.gn

@@ -37,6 +37,7 @@ source_set("first_run") {
     "//ios/chrome/browser/ui/authentication",
     "//ios/chrome/browser/ui/authentication/signin",
     "//ios/chrome/browser/ui/commands",
+    "//ios/chrome/browser/ui/elements",
     "//ios/chrome/browser/ui/fancy_ui",
     "//ios/chrome/browser/ui/icons",
     "//ios/chrome/browser/ui/material_components",