Version: 53.0.2785.4 (also ToT)

What steps will reproduce the problem?
(1) In the omnibox, type chrome://md-settings/searchEngines
(2) Press Enter, then quickly Ctrl+T to open a new tab
(3) Wait for the first tab (Settings) to finish loading
(4) Switch back to the first tab (Settings)

Expected: The "Manage search engines" sub-page is full-height.

Actual: The "Manage search engines" sub-page is shown within the "Search engine" section, along with the rest of the Basic page.

Console error: Cannot read property 'scrollTop' of null" (at main_page_behavior.js:112)

I'll address  this once https://codereview.chromium.org/2106013002/ lands.