add accessibility descriptions/events

    Bug: 4979091
    added content descriptions to the image buttons
    send event for screen transition

Change-Id: I403fe8504cace4aa84a5b1c6ca18f6c10fc9be34
diff --git a/res/layout/title_bar_nav.xml b/res/layout/title_bar_nav.xml
index 5a3c10e..5e4a3a1 100644
--- a/res/layout/title_bar_nav.xml
+++ b/res/layout/title_bar_nav.xml
@@ -49,6 +49,7 @@
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_gravity="center_vertical"
+            android:contentDescription="@string/accessibility_button_stop"
             android:src="@drawable/ic_stop_holo_dark"
             style="@style/HoloButton" />
         <com.android.browser.UrlInputView
@@ -73,6 +74,7 @@
             android:id="@+id/voice"
             android:layout_width="wrap_content"
             android:layout_height="match_parent"
+            android:contentDescription="@string/accessibility_button_voice"
             android:src="@drawable/ic_voice_search_holo_dark"
             style="@style/HoloButton"
             android:visibility="gone" />
@@ -81,6 +83,7 @@
         android:id="@+id/tab_switcher"
         android:layout_width="wrap_content"
         android:layout_height="match_parent"
+            android:contentDescription="@string/accessibility_button_navscreen"
         android:src="@drawable/ic_windows_holo_dark"
         style="@style/HoloButton" />
     <ImageButton
@@ -89,5 +92,6 @@
         android:layout_height="match_parent"
         style="@style/HoloButton"
         android:gravity="center_vertical"
+        android:contentDescription="@string/accessibility_button_more"
         android:src="@*android:drawable/ic_menu_moreoverflow_normal_holo_dark" />
 </com.android.browser.NavigationBarPhone>