Merge pull request #19769 from wordpress-mobile/enhancement/reader-scroll-to-top

[Reader] Scroll to the top if the tab bar button is tapped

Author: twstokes

RELEASE-NOTES.txt

@@ -6,6 +6,7 @@
 * [***] You can now migrate your site content to the Jetpack app without a hitch. [#19759]
 * [**] [internal] Upgrade React Native from 0.66.2 to 0.69.4 [https://github.com/wordpress-mobile/gutenberg-mobile/pull/5193]
 * [*] [internal] When a user migrates to the Jetpack app and allows notifications, WordPress app notifications are disabled. [#19616, #19611, #19590]
+* [*] Reader now scrolls to the top if the tab bar button is tapped. [#19769]
 
 21.3
 -----

WordPress/Classes/ViewRelated/Reader/Tab Navigation/ReaderTabViewController.swift

@@ -198,3 +198,14 @@ extension ReaderTabViewController {
         static let spotlightOffset = UIOffset(horizontal: 20, vertical: -10)
     }
 }
+
+// MARK: - WPScrollableViewController conformance
+extension ReaderTabViewController: WPScrollableViewController {
+    /// Scrolls the first child VC to the top if it's a `ReaderStreamViewController`.
+    func scrollViewToTop() {
+        guard let readerStreamVC = children.first as? ReaderStreamViewController else {
+            return
+        }
+        readerStreamVC.scrollViewToTop()
+    }
+}