MD Settings: convert paper-icon-button to paper-icon-button-light.

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). */
       }
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         align-items: center;
         flex: auto;
       }
 
       .no-outline,
       [scrollable] .no-outline {
         background: none;
         outline: none;
       }
 
+      /* Prevent icon-button's ripples from fighting with potential scrollbars.
+       * Also apply to all iron-lists to align the buttons across them all.*/
+      [scrollable],
+      .scroll-container,
+      iron-list {
+        --cr-paper-icon-button-margin: {
+          -webkit-margin-start: 0;
+          -webkit-margin-end: 0;
+        };
+      }
+
       /* Helper for a list frame to automatically avoid the separator line. */
       .vertical-list > *:not(:first-of-type) {
         border-top: var(--settings-separator-line);
       }
 
       /* The separator a vertical line like a horizontal rule <hr> tag, but goes
        * the other way. An example is near the |sign out| button on the People
        * settings. */
       :-webkit-any(.settings-box, .list-item) .separator {
         -webkit-border-start: var(--settings-separator-line);
         -webkit-margin-end: var(--settings-box-row-padding);
         -webkit-margin-start: var(--settings-box-row-padding);
         flex-shrink: 0;
         --settings-separator-gaps: 9px;
         height: calc(var(--settings-row-min-height) -
             var(--settings-separator-gaps));
       }
 
       :-webkit-any(.settings-box, .list-item).two-line .separator {
         height: calc(var(--settings-row-two-line-min-height) -
             2 * var(--settings-separator-gaps));
       }
 
+
+      /* Avoid too much margin from both .separator and the button */
+      .separator + button[is='paper-icon-button-light'] {
+        --cr-paper-icon-button-margin: {
+          --webkit-margin-start: 0;
+        };
+      }
+
       .settings-checkbox-spacer {
         -webkit-margin-start: calc(
             var(--checkbox-margin-start) +
             var(--checkbox-size) +
             var(--settings-control-spacing));
       }
 
       .favicon-image {
         background-repeat: no-repeat;
         background-size: contain;
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         transform: rotate(-135deg);
       }
 
       .column-header {
         color: var(--paper-grey-600);
         font-weight: 500;
       }
     </style>
   </template>
 </dom-module>