Add content description for the expand button.

Bug: 1122697
Change-Id: I828b21a122241bcbf76954d47bf6d789ea31dc1d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2380419Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Xinghui Lu <xinghuilu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802718}

components/browser_ui/strings/android/browser_ui_strings.grd

@@ -331,6 +331,9 @@
       <message name="IDS_ACCESSIBILITY_CANCEL_SELECTION" desc="Content description for the cancel selection button that deselects the selected items in a selectable list view.">
         Cancel selection
       </message>
+      <message name="IDS_ACCESSIBILITY_EXPAND_BUTTON" desc="Content description for the expand button in the expand_arrow_with_separator layout.">
+        Expand
+      </message>
 
       <message name="IDS_SELECTED_ITEMS" desc="Content description for a number indicating how many items are selected. [ICU Syntax]">
         {NUM_SELECTED, plural,

components/browser_ui/strings/android/browser_ui_strings_grd/IDS_ACCESSIBILITY_EXPAND_BUTTON.png.sha1

+435925989dd5756eed78e49b301627aba7e149db

components/browser_ui/widget/android/java/res/layout/expand_arrow_with_separator.xml

@@ -26,5 +26,6 @@
         android:paddingEnd="@dimen/radio_button_with_description_lateral_padding"
         android:src="@drawable/ic_expand_more_horizontal_black_24dp"
         android:background="?android:attr/selectableItemBackground"
+        android:contentDescription="@string/accessibility_expand_button"
         app:tint="@color/default_icon_color_tint_list"/>
 </LinearLayout>