Download location: hide the radio button if there is no SD card option.

This CL hides the radio button when there is only default download
directory option.

Also tweaks the layout a little bit, so the radio button and the text
can align with the "Download location" title in the preference UI.


Bug: 850586
Change-Id: Id686ee8e8d06bd477606f62741386095fa11c31c
Reviewed-on: https://chromium-review.googlesource.com/1098296Reviewed-by: David Trainor <dtrainor@chromium.org>
Commit-Queue: Xing Liu <xingliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567050}

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

@@ -15,8 +15,8 @@
         android:id="@+id/radio_button"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:layout_marginStart="6dp"
-        android:layout_marginEnd="16dp"
+        android:layout_marginStart="10dp"
+        android:layout_marginEnd="6dp"
         android:importantForAccessibility="no" />
 
     <LinearLayout
@@ -24,6 +24,7 @@
         android:layout_height="wrap_content"
         android:layout_weight="1"
         android:orientation="vertical"
+        android:layout_marginStart="10dp"
         android:layout_gravity="center_vertical" >
         <TextView
             android:id="@+id/title"

chrome/android/java/src/org/chromium/chrome/browser/preferences/download/DownloadLocationPreferenceAdapter.java

@@ -57,6 +57,9 @@ public class DownloadLocationPreferenceAdapter
         radioButton.setTag(position);
         radioButton.setOnClickListener(this);
 
+        // Only show the radio button when there are multiple items.
+        if (getCount() <= 1) radioButton.setVisibility(View.GONE);
+
         view.setEnabled(isEnabled(position));
 
         DirectoryOption directoryOption = (DirectoryOption) getItem(position);