MD Extension A11y: Label 'on' toggle in Extension Details.

Bug: 764125
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: If131619735e2e81b6d45837616b5a4e56ff6173f
Reviewed-on: https://chromium-review.googlesource.com/740823
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Reviewed-by: Dave Schuyler <dschuyler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512584}

chrome/browser/resources/md_extensions/detail_view.html

@@ -195,6 +195,11 @@
                 icon-aria-label="[[data.controlledInfo.type]]">
             </cr-tooltip-icon>
             <cr-toggle id="enable-toggle"
+                aria-label$="[[appOrExtension(
+                    data.type,
+                    '$i18nPolymer{appEnabled}',
+                    '$i18nPolymer{extensionEnabled}')]]"
+                aria-describedby="name"
                 checked="[[isEnabled_(data.state)]]"
                 on-change="onEnableChange_"
                 disabled="[[!isEnableToggleEnabled_(data.*)]]">