Update "Open in Browser" dialog to meet a11y guideline

* Updating OK button to be 48dp height
* Updating line height of description text so that when font size is
  max, words don't overlap

Fix: 397859648
Fix: 397866754
Test: Open Youtube in desktop windowing and click gear icon to launch
dialog
Flag: EXEMPT bugfix

Change-Id: I3e6beae488bc6856930c3a401e5e6798d11cc7fc