MD Settings: make .{primary,secondary,tertiary}-button selectors less specific

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">
       h2 {
         align-items: center;
         display: flex;
@@ skipping 69 matching lines @@
       }
 
       span ~ a {
         -webkit-margin-start: 4px;
       }
 
       [is='action-link'],
       [is='action-link']:active,
       [is='action-link']:hover,
       [is='action-link']:visited,
-      paper-button.primary-button,
-      paper-button.tertiary-button {
+      .primary-button,
+      .tertiary-button {
         color: var(--google-blue-700);
       }
 
-      paper-button.primary-button,
-      paper-button.tertiary-button {
+      .primary-button,
+      .tertiary-button {
         --paper-button-flat-keyboard-focus: {
           background-color: rgba(51, 103, 214, .12);  /* --google-blue-700 */
         };
       }
 
       [is='action-link']:hover {
         text-decoration: none;
       }
 
       /* 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. */
-      paper-button.primary-button {
+      .primary-button {
         --paper-button: {
           font-weight: 500;
           text-align: start;
         };
       }
 
       /* See notes in .primary-button. */
-      paper-button.secondary-button {
+      .secondary-button {
         --paper-button: {
           color: var(--paper-grey-600);
           text-decoration: none;
           font-weight: 500;
         };
         --paper-button-flat-keyboard-focus: {
           background-color: rgba(0, 0, 0, .12);
         };
       }
 
       /* See notes in .primary-button. */
-      paper-button.tertiary-button {
+      .tertiary-button {
         --paper-button: {
           font-weight: 400;
           text-decoration: none;
         };
       }
 
-      .settings-box paper-button.primary-button,
-      .settings-box paper-button.secondary-button,
-      .settings-box paper-button.secondary-button {
+      .settings-box .primary-button,
+      .settings-box .secondary-button,
+      .settings-box .secondary-button {
         margin-left: -12px;
         margin-right: -12px;
         padding-left: 12px;
         padding-right: 12px;
       }
 
       paper-checkbox {
         --paper-checkbox-checked-color: var(--google-blue-500);
         --paper-checkbox-label-spacing: var(--checkbox-spacing);
         --paper-checkbox-size: var(--checkbox-size);
@@ skipping 186 matching lines @@
 
       .favicon-image {
         background-repeat: no-repeat;
         background-size: contain;
         height: 16px;
         width: 16px;
       }
     </style>
   </template>
 </dom-module>