🛃 Get correct views when updating CustomTabToolbar action buttons.

Bug: b/73149793
Change-Id: I9ea2bd9d8bef021b2d36d4eb49d2a5bf74da2f8e
Reviewed-on: https://chromium-review.googlesource.com/911669Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Commit-Queue: Bernhard Bauer <bauerb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#535861}

chrome/android/java/src/org/chromium/chrome/browser/toolbar/CustomTabToolbar.java

@@ -215,7 +215,7 @@ public class CustomTabToolbar extends ToolbarLayout implements LocationBar,
 
     @Override
     public void updateCustomActionButton(int index, Drawable drawable, String description) {
-        ImageButton button = (ImageButton) getChildAt(index);
+        ImageButton button = (ImageButton) mCustomActionButtons.getChildAt(index);
         assert button != null;
         updateCustomActionButtonVisuals(button, drawable, description);
     }