fix(material/tooltip): Allow typography mixin to consume 2018 style configs

See angular#21059 for context.

Author: mmalerba

src/material/tooltip/_tooltip-theme.scss

@@ -1,5 +1,6 @@
 @import '../core/theming/palette';
 @import '../core/theming/theming';
+@import '../core/typography/typography';
 @import '../core/typography/typography-utils';
 
 $mat-tooltip-target-height: 22px;
@@ -21,6 +22,7 @@ $mat-tooltip-handset-vertical-padding:
 }
 
 @mixin mat-tooltip-typography($config-or-theme) {
+  $config: mat-private-typography-normalized-config(mat-get-typography-config($config-or-theme));
   $config: mat-get-typography-config($config-or-theme);
   .mat-tooltip {
     font-family: mat-font-family($config);