Inherit default text color from MainTheme.

chrome/android/java/res/layout/signin_and_sync_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. -->
 <org.chromium.chrome.browser.signin.SigninAndSyncView
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:chrome="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:orientation="vertical"
     android:padding="16dp" >
 
     <TextView
         android:id="@+id/title"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginBottom="8dp"
-        android:textColor="@color/default_text_color"
         android:textSize="16sp"
         android:textStyle="bold" />
 
     <TextView
         android:id="@+id/description"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
-        android:textColor="@color/default_text_color"
         android:textSize="14sp" />
 
     <LinearLayout
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginTop="16dp"
         android:layout_gravity="end"
         android:gravity="center_vertical"
         android:orientation="horizontal" >
 
@@ skipping 11 matching lines @@
             android:id="@+id/sign_in"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
             android:textAllCaps="true"
             android:textColor="@android:color/white"
             android:textSize="15sp"
             chrome:buttonColor="@color/light_active_color" />
     </LinearLayout>
 
 </org.chromium.chrome.browser.signin.SigninAndSyncView>