Inherit default text color from MainTheme.

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

 <?xml version="1.0" encoding="utf-8"?>
 <!-- Copyright 2016 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 10 matching lines @@
         android:layout_marginEnd="16dp"
         android:contentDescription="@null"/>
 
     <TextView
         android:id="@+id/account_name"
         android:layout_width="0dp"
         android:layout_height="wrap_content"
         android:layout_weight="1"
         android:minHeight="56dp"
         android:gravity="center_vertical"
-        android:textColor="@color/default_text_color"
         android:textSize="@dimen/fre_normal_text_size"/>
 
     <ImageView
         android:id="@+id/account_selection_mark"
         android:layout_width="24dp"
         android:layout_height="24dp"
         android:layout_marginStart="16dp"
         android:src="@drawable/ic_check_googblue_24dp"
         android:contentDescription="@null"
         android:visibility="gone"/>
 </LinearLayout>