[MD settings] move root css vars; increase checkbox and h2 row-height

chrome/browser/resources/settings/settings_root_css.html

+<!-- Common css variables for Material Design settings. -->
+<style is="custom-style">
+  :root {
+    --checkbox-margin-start: 2px;
+    --checkbox-size: 16px;
+    --checkbox-spacing: 18px;
+    --iron-icon-fill-color: var(--paper-grey-600);
+    --iron-icon-height: 20px;
+    --iron-icon-spacing: 16px;
+    --iron-icon-width: 20px;
+    --paper-checkbox-label-color: inherit;
+    --paper-dialog-color: inherit;
+    --paper-icon-button: {
+      width: 36px;
+      height: 36px;
+    };
+    --paper-input-max-width: 264px;
+    --paper-item: {
+      font-size: inherit;
+    };
+    --paper-radio-button-label-color: inherit;
+    --paper-radio-group-item-padding: 0;
+
+    /* Custom grey for Alan (bettes@). */
+    --settings-background-color: rgb(241, 241, 241);
+    --settings-secondary: {
+      color: var(--paper-grey-600);
+      font-weight: 400;
+      margin-top: 4px;
+    };
+    --settings-error-color: var(--paper-red-700);
+    --settings-hover-color: var(--google-grey-300);
+
+    /* Some colors use non-MD colors.  These custom colors are specified by
+     * UX design (bettes@). */
+    --settings-nav-grey: rgb(90, 90, 90);
+
+    --settings-row-min-height: 44px;
+    --settings-separator-line: 1px solid rgba(0, 0, 0, 0.06);
+
+    --settings-title-bar-background-color: var(--google-blue-700);
+    --settings-title-bar-color: rgb(255, 255, 255);
+    --settings-title-search-color: rgb(192, 199, 205);
+  }
+</style>