MD Settings: Fix several global UI polish bugs.

chrome/browser/resources/settings/settings_shared_css.html

 <link rel="import" href="chrome://resources/cr_elements/shared_style_css.html">
 <link rel="import" href="/settings_vars_css.html">
 
 <!-- Common styles for Material Design settings. -->
 <dom-module id="settings-shared">
   <template>
     <style include="cr-shared-style">
       /* Included here so we don't have to include "iron-positioning" in every
        * stylesheet. See crbug.com/498405. */
       [hidden] {
@@ skipping 22 matching lines @@
       }
 
       iron-icon[icon='cr:check'],
       iron-icon[icon='settings:done'] {
        --iron-icon-fill-color: var(--google-green-500);
       }
 
       paper-button {
         height: 32px;
         margin: 0;
+        border-radius: 4px;
       }
 
       paper-button[toggles][active] {
         background-color: var(--paper-grey-300);
       }
 
       paper-toggle-button {
         @apply(--settings-actionable);
         height: var(--settings-row-min-height);
         width: 31px;
@@ skipping 193 matching lines @@
         border-top: var(--settings-separator-line);
         display: flex;
         min-height: var(--settings-box-min-height);
         padding: 0 var(--settings-box-row-padding);
       }
 
       .settings-box.two-line {
         min-height: var(--settings-box-two-line-min-height);
       }
 
+      .settings-box.three-line {
+        min-height: var(--settings-box-three-line-min-height);
+      }
+
       /* We use an explicit tag to remove the top border, rather than a
        * :first-of-type modifier. This is a conscious choice, please consult
        * with dbeam@ or dschuyler@ prior to changing it. */
       .settings-box.first,
       .settings-box.continuation {
         border-top: none;
       }
 
       .settings-box.block {
         display: block;
@@ skipping 115 matching lines @@
       /* Turns the arrow direction downwards, when the bubble is placed above
        * the anchor element */
       .search-bubble-innards.above::after {
         -webkit-transform: rotate(-135deg);
         bottom: -5px;
         top: auto;
       }
     </style>
   </template>
 </dom-module>