[MD settings] set margins on change download location button

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">
       :host-context([dir=rtl]) button[is='paper-icon-button-light'] {
         transform: scaleX(-1);  /* Flip on the X axis (aka mirror). */
       }
@@ skipping 55 matching lines @@
       .primary-button {
         --paper-button-flat-keyboard-focus: {
           background: rgba(51, 103, 214, .12);  /* --google-blue-700 */
         };
       }
 
       a[href] {
         text-decoration: none;
       }
 
-      /* For elements that are simple outlinks but dont look like anchors. */
+      /* For elements that are simple out-links but don't look like anchors. */
       .inherit-color {
         color: inherit !important;
       }
 
       /* There are three main button styles, .primary-button, .secondary-button,
        * and .tertiary-button. The primary is the action button (e.g. "edit",
        * "delete") while the secondary is often a "Cancel" button. A tertiary
        * button may be used to get more information or similar, that we expect
        * most users will not need. */
       .primary-button {
         --paper-button: {
+          -webkit-padding-end: var(--settings-button-edge-spacing);
+          -webkit-padding-start: var(--settings-button-edge-spacing);
           font-weight: 500;
           text-align: start;
         };
       }
 
       .primary-toggle {
         color: var(--paper-grey-600);
         font-weight: 500;
       }
 
       .primary-toggle[checked] {
         color: var(--google-blue-500);
       }
 
       /* See notes in .primary-button. */
       .secondary-button {
         --paper-button: {
+          -webkit-padding-end: var(--settings-button-edge-spacing);
+          -webkit-padding-start: var(--settings-button-edge-spacing);
           color: var(--paper-grey-600);
           font-weight: 500;
           min-width: 1em;  /* A tighter fit than 5.14em for short buttons. */
           text-decoration: none;
         };
         --paper-button-flat-keyboard-focus: {
           background: rgba(0, 0, 0, .12);
         };
       }
 
       .settings-box .primary-button,
-      .settings-box .secondary-button,
       .settings-box .secondary-button {
-        -webkit-margin-end: -12px;
-        -webkit-margin-start: -12px;
-        -webkit-padding-end: 12px;
-        -webkit-padding-start: 12px;

[dschuyler, 2017/05/08 23:35:04]

Moving the padding to the .primary-button and .secondary-button applies the
padding to settings-controlled-button as well (which is desired).

The other change is moving from using 12/-12px to using a variable.

+        -webkit-margin-end: calc(var(--settings-button-edge-spacing) * -1);
+        -webkit-margin-start: calc(var(--settings-button-edge-spacing) * -1);
       }
 
       paper-checkbox {
         --paper-checkbox-checked-color: var(--google-blue-500);
         --paper-checkbox-label-spacing: var(--settings-control-spacing);
         --paper-checkbox-size: var(--checkbox-size);
         --paper-checkbox-unchecked-color: var(--paper-grey-600);
         -webkit-margin-start: var(--checkbox-margin-start);
       }
 
@@ skipping 268 matching lines @@
         transform: rotate(-135deg);
       }
 
       .column-header {
         color: var(--paper-grey-600);
         font-weight: 500;
       }
     </style>
   </template>
 </dom-module>