Download location: disable accessibility for the radio button.

This CL disables the accessibility event for the radio button, since the
text view is selectable and also inform "Double click to select" in
talk back, and the radio button will make user confusing.

Bug: 850254
Change-Id: I41270c62c7dbabc073d2a5317cb505ee42d890c6
Reviewed-on: https://chromium-review.googlesource.com/1093720
Reviewed-by: Min Qin <qinmin@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566256}

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

@@ -16,7 +16,8 @@
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginStart="6dp"
-        android:layout_marginEnd="16dp" />
+        android:layout_marginEnd="16dp"
+        android:importantForAccessibility="no" />
 
     <LinearLayout
         android:layout_width="0dp"