[Android] Allow setting recently visited search engines as default search engine

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

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2015 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. -->
 
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:background="?android:attr/selectableItemBackground"
     android:gravity="center_vertical"
     android:orientation="horizontal"
     android:padding="6dp">
 
     <android.widget.RadioButton
         android:id="@+id/radiobutton"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginEnd="21dp"
         android:clickable="false" />
 
     <LinearLayout
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_weight="1"
         android:orientation="vertical">
         <TextView
             android:id="@+id/description"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:textSize="17sp" />
+            android:textSize="17sp"
+            android:textColor="#000000" />
+        <TextView
+            android:id="@+id/url"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:textSize="16sp"
+            android:textColor="#646464" />

[gone, 2016/11/01 21:30:29]

@color/descriptive_text_color

[ltian, 2016/11/01 22:59:36]

Done.

         <TextView
             android:id="@+id/link"

[gone, 2016/11/01 21:30:29]

These TextViews should be renamed: the "description" is actually the name of the
search engine, and the "link" is more or less clarification text.

[ltian, 2016/11/01 22:59:36]

Done.

             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_marginBottom="-12dp"
             android:layout_marginTop="-12dp"
             android:gravity="center_vertical"
             android:minHeight="48dp"
             android:paddingBottom="12dp"
             android:paddingTop="12dp" />

[gone, 2016/11/01 21:30:29]

This should have the color set, right?

android:textColor="@color/light_active_color"

[ltian, 2016/11/01 22:59:36]

The color setting is coded in SearchEngineAdapter.java by "ForegroundColorSpan
linkSpan = new ForegroundColorSpan(
                    ApiCompatibilityUtils.getColor(resources,
R.color.pref_accent_color));" and R.color.pref_accent_color =
@color/light_active_color.

     </LinearLayout>
 
 </LinearLayout>