Fix styling of Form-Not-Secure warnings on Android

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"
     android:gravity="center_vertical"
     android:orientation="horizontal" >
 
     <!-- These layout params are overwritten in DropdownAdapter.java -->
     <ImageView
         android:id="@+id/start_dropdown_icon"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:layout_margin="8dp"
+        android:layout_margin="@dimen/dropdown_icon_margin"
         android:contentDescription="@null" />
 
     <LinearLayout
         android:id="@+id/dropdown_label_wrapper"
         android:layout_width="0dp"
         android:layout_height="0dp"
         android:layout_weight="1"
         android:gravity="center_vertical"
         android:orientation="vertical" >
 
@@ skipping 14 matching lines @@
             android:id="@+id/dropdown_sublabel"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:layout_marginEnd="10dp"
             android:layout_marginStart="10dp"
             android:ellipsize="end"
             android:includeFontPadding="false"
             android:singleLine="true"
             android:textAlignment="viewStart"
             android:textColor="#646464"
-            android:textSize="14sp" />
+            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>