Add content description to navigation button on settings toolbar.

app/src/main/res/layout/dsl_settings_toolbar.xml

@@ -14,6 +14,7 @@
         app:layout_constraintTop_toTopOf="parent"
         app:navigationIcon="@drawable/ic_arrow_left_24"
         app:titleTextAppearance="@style/Signal.Text.Title"
+        app:navigationContentDescription="@string/DSLSettingsToolbar__navigate_up"
         tools:title="Settings" />
 
     <View

app/src/main/res/values/strings.xml

@@ -3673,6 +3673,9 @@
     <string name="ContactSelectionListItem__sms">SMS</string>
     <string name="ContactSelectionListItem__dot_s">· %1$s</string>
 
+    <!-- DSLSettingsToolbar -->
+    <string name="DSLSettingsToolbar__navigate_up">Navigate up</string>
+
     <!-- EOF -->
 
 </resources>