[Merge M57] Use uniform margin for icon, label and sublabel

ui/android/java/res/layout/dropdown_item.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.
 -->
 
 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
@@ skipping 26 matching lines @@
             android:includeFontPadding="false"
             android:singleLine="true"
             android:textAlignment="viewStart"
             android:textColor="@drawable/dropdown_label_color"
             android:textSize="@dimen/dropdown_item_label_font_size" />
 
         <TextView
             android:id="@+id/dropdown_sublabel"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:layout_marginEnd="10dp"
-            android:layout_marginStart="10dp"
+            android:layout_marginEnd="@dimen/dropdown_item_label_margin"
+            android:layout_marginStart="@dimen/dropdown_item_label_margin"
             android:ellipsize="end"
             android:includeFontPadding="false"
             android:singleLine="true"
             android:textAlignment="viewStart"
             android:textColor="#646464"
             android:textSize="@dimen/dropdown_item_sublabel_font_size" />
     </LinearLayout>
 
     <ImageView
         android:id="@+id/end_dropdown_icon"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_margin="8dp"
         android:contentDescription="@null" />
 
 </LinearLayout>