MD Settings: fix size of broken people icon

R=tommycli@chromium.org
BUG=638534
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2256813003
Cr-Commit-Position: refs/heads/master@{#412632}

chrome/browser/resources/settings/people_page/people_page.html

@@ -39,6 +39,7 @@
       #profile-icon {
         background-position: center;
         background-repeat: no-repeat;
+        background-size: cover;
         border-radius: 20px;
         height: 40px;
         width: 40px;