Reading List: Mark entry read when opening external app.

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index 5204ae4a1656e50bb3cc2cd284f5a327bef4315b..db6cffdf7ae4ce04b3e502c70d52360a2060232a 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -3063,6 +3063,8 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
     if (![self shouldOpenExternalURLForNavigationAction:action]) {
       return NO;
     }
+    web::NavigationItem* item = self.currentNavItem;
+    GURL sourceURL = item ? item->GetOriginalRequestURL() : GURL::EmptyGURL();
 
     // Stop load if navigation is believed to be happening on the main frame.
     if ([self isMainFrameNavigationAction:action])
@@ -3084,6 +3086,7 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
     }
 
     if ([_delegate openExternalURL:requestURL
+                         sourceURL:sourceURL
                        linkClicked:isNavigationTypeLinkActivated]) {
       // Record the URL so that errors reported following the 'NO' reply can be
       // safely ignored.