Accessibility strings for app install alerts

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

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2014 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.
 -->
 
 <org.chromium.chrome.browser.banners.AppBannerView
         xmlns:android="http://schemas.android.com/apk/res/android"
         android:id="@+id/app_banner_view"
         android:background="@drawable/card_background_default"
+        android:clickable="true"
+        android:focusableInTouchMode="true"
         android:layout_width="match_parent"
         android:layout_height="wrap_content">
     <!-- View showing the icon. -->
     <ImageView
             android:id="@+id/app_icon"
             android:adjustViewBounds="true"
             android:layout_width="wrap_content"
             android:layout_height="@dimen/app_banner_icon_size"
             android:layout_marginEnd="@dimen/app_banner_icon_margin_end" />
 
@@ skipping 38 matching lines @@
     <!-- View showing how well the app is rated. -->
     <org.chromium.chrome.browser.banners.RatingView
             android:id="@+id/app_rating"
             android:adjustViewBounds="true"
             android:layout_width="wrap_content"
             android:layout_height="@dimen/app_banner_star_height" />
 
     <!-- Button that closes the banner. -->
     <ImageButton
             android:id="@+id/close_button"
+            android:contentDescription="@string/infobar_close"
             android:adjustViewBounds="true"
             android:src="@drawable/dismiss"
             android:background="@drawable/app_banner_button_close"
             android:padding="@dimen/app_banner_close_button_padding"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"/>
 
     <!-- View covering the entire banner.  Used to indicate the banner is highlighted. -->
     <View
             android:id="@+id/banner_highlight"
             android:background="@color/app_banner_card_highlight"
             android:visibility="gone"
             android:layout_width="match_parent"
             android:layout_height="match_parent" />
 </org.chromium.chrome.browser.banners.AppBannerView>