[MD settings] set margins on change download location button

chrome/browser/resources/settings/settings_shared_css.html

Index: chrome/browser/resources/settings/settings_shared_css.html
diff --git a/chrome/browser/resources/settings/settings_shared_css.html b/chrome/browser/resources/settings/settings_shared_css.html
index d3c060bed0c11454731d4c70775c161c756403ea..07424c33e8cf674e36cb39435d96e4b904a223fb 100644
--- a/chrome/browser/resources/settings/settings_shared_css.html
+++ b/chrome/browser/resources/settings/settings_shared_css.html
@@ -73,7 +73,7 @@
         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;
       }
@@ -85,6 +85,8 @@
        * 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;
         };
@@ -102,6 +104,8 @@
       /* 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. */
@@ -113,12 +117,9 @@
       }
 
       .settings-box .primary-button,
-      .settings-box .secondary-button,
       .settings-box .secondary-button {

[hcarmona, 2017/05/09 17:32:01]

------------------------------------------------------------------------
Can we put this here so it's a bit more obvious that the padding and
margin are related in both the primary and secondary buttons?

--paper-button: {
  -webkit-padding-end: var(--settings-button-edge-spacing);
  -webkit-padding-start: var(--settings-button-edge-spacing);
}

[dschuyler, 2017/05/09 18:15:09]

Like redundantly for emphasis? I'm concerned that may open up including other
style info too (I guess I'm making a 'slippery slope' argument, which is a bad
argument I acknowledge).

[hcarmona, 2017/05/09 18:55:59]

No, I looked into mixins. I thought they stacked, but adding a
--paper-button here will override the other values.
I'd rather not move this up b/c it would cause duplication.

-        -webkit-margin-end: -12px;
-        -webkit-margin-start: -12px;
-        -webkit-padding-end: 12px;
-        -webkit-padding-start: 12px;
+        -webkit-margin-end: calc(var(--settings-button-edge-spacing) * -1);
+        -webkit-margin-start: calc(var(--settings-button-edge-spacing) * -1);
       }
 
       paper-checkbox {