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

ui/webui/resources/cr_elements/cr_icons_css.html

+<link rel="import" href="chrome://resources/html/polymer.html">
+
+<!-- Common icon classes for Material Design WebUI. -->
+<dom-module id="cr-icons">
+  <template>
+    <style>
+      button[is='paper-icon-button-light'].subpage-arrow,
+      paper-icon-button.subpage-arrow {
+        background-image: url(../images/arrow_right.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-cancel {
+        background-image: url(../images/icon_cancel.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-cancel-toolbar {
+        background-image: url(../images/icon_cancel_toolbar.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-clear {
+        background-image: url(../images/icon_clear.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-delete {
+        background-image: url(../images/icon_delete.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-external {
+        background-image: url(../images/open_in_new.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-more-vert {
+        background-image: url(../images/icon_more_vert.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-settings {
+        background-image: url(../images/icon_settings.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-search {
+        background-image: url(../images/icon_search.svg);
+      }
+
+      button[is='paper-icon-button-light'].icon-arrow-dropdown {
+        background-image: url(../images/icon_arrow_dropdown.svg);
+      }
+    </style>
+  </template>
+</dom-module>