Fix some new tanslate infobar UI bugs

chrome/android/java/res/layout/infobar_translate_compact_content.xml

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2017 The Chromium Authors. All rights reserved.
      Use of this source code is governed by a BSD-style license that can be
      found in the LICENSE file. -->
 
-<!-- TODO(googleo): Add correct style based on spec and contentDescription. -->
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:id="@+id/translate_infobar_content"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:gravity="center_vertical"
     android:orientation="horizontal">
 
     <org.chromium.chrome.browser.infobar.translate.TranslateTabLayout
         android:id="@+id/translate_infobar_tabs"
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_weight="1"
         android:requiresFadingEdge="horizontal"
         android:fadingEdgeLength="@dimen/infobar_translate_fade_edge_length"
         app:tabIndicatorColor="@color/infobar_accent_blue"
         app:tabSelectedTextColor="@color/infobar_accent_blue"
         app:tabGravity="fill"
         app:tabMode="scrollable" />
 
     <org.chromium.chrome.browser.widget.TintedImageButton
         android:id="@+id/translate_infobar_menu_button"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:minHeight="@dimen/min_touch_target_size"
         android:minWidth="@dimen/min_touch_target_size"
         android:scaleType="center"
         android:background="?attr/selectableItemBackground"
-        android:contentDescription="@null"
+        android:contentDescription="@string/accessibility_toolbar_btn_menu"
         android:src="@drawable/btn_menu"
         app:tint="@color/dark_mode_tint" />
 </LinearLayout>