MDL-74136 theme_boost: Display blocks drawer icon properly on RTL

lib/classes/output/icon_system_fontawesome.php

@@ -359,6 +359,7 @@ class icon_system_fontawesome extends icon_system_font {
             'core:t/block_to_dock_rtl' => 'fa-chevron-right',
             'core:t/block_to_dock' => 'fa-chevron-left',
             'core:t/blocks_drawer' => 'fa-chevron-left',
+            'core:t/blocks_drawer_rtl' => 'fa-chevron-right',
             'core:t/calc_off' => 'fa-calculator', // TODO: Change to better icon once we have stacked icon support or more icons.
             'core:t/calc' => 'fa-calculator',
             'core:t/check' => 'fa-check',

theme/boost/templates/drawers.mustache

@@ -120,7 +120,8 @@
                             title="{{#str}}opendrawerblocks, core{{/str}}"
                         >
                             <span class="sr-only">{{#str}}opendrawerblocks, core{{/str}}</span>
-                            {{#pix}}t/blocks_drawer, core{{/pix}}
+                            <span class="dir-rtl-hide">{{#pix}}t/blocks_drawer, core{{/pix}}</span>
+                            <span class="dir-ltr-hide">{{#pix}}t/blocks_drawer_rtl, core{{/pix}}</span>
                         </button>
                     </div>
                 {{/hasblocks}}