Use ButtonCompat to get Material-y buttons in more places.

chrome/android/java/res/values-v21/styles.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. -->
 
 <resources>
     <!-- Preferences -->
     <style name="PreferencesTheme" parent="ThemeWithActionBar">
         <item name="android:textColorLink">@color/pref_accent_color</item>
-        <item name="android:buttonStyle">@style/PreferenceButtonStyle</item>
         <item name="android:alertDialogTheme">@style/PreferencesDialogTheme</item>
-        <item name="android:colorButtonNormal">@color/btn_default_preferences</item>
         <item name="android:editTextBackground">@drawable/abc_edit_text_material</item>
         <item name="android:editTextStyle">@style/PreferenceEditTextStyle</item>
         <item name="android:spinnerItemStyle">@style/PreferenceSpinnerItem</item>
         <item name="floatLabelTextAppearance">@style/PreferenceFloatLabelTextAppearance</item>
         <item name="floatLabelPaddingLeft">@dimen/pref_autofill_field_horizontal_padding</item>
         <item name="floatLabelPaddingRight">@dimen/pref_autofill_field_horizontal_padding</item>
         <item name="floatLabelPaddingTop">@dimen/pref_autofill_field_top_padding</item>
     </style>
     <style name="PreferencesDialogTheme" parent="@android:style/Theme.Material.Light.Dialog.Alert">
         <item name="android:colorAccent">@color/pref_accent_color</item>
     </style>
-    <style name="PreferenceButtonStyle" parent="@android:style/Widget.Material.Light.Button">
-        <item name="android:textColor">#fff</item>
-    </style>
     <style name="PreferenceCategoryWithButtonStyle">
         <item name="android:paddingStart">?android:attr/listPreferredItemPaddingStart</item>
         <item name="android:paddingEnd">4dp</item>
     </style>
     <style name="PreferenceCategoryTextStyle">
         <item name="android:fontFamily">sans-serif-medium</item>
         <item name="android:textColor">@color/pref_accent_color</item>
         <item name="android:textSize">14sp</item>
     </style>
     <style name="PreferenceEditTextStyle" parent="Widget.AppCompat.EditText">
@@ skipping 21 matching lines @@
     <!-- Buttons -->
     <style name="ButtonCompat" parent="ButtonCompatBase">
         <item name="android:background">@drawable/button_compat</item>
         <item name="android:fontFamily">sans-serif-medium</item>
     </style>
     <style name="ButtonBorderlessCompat" parent="ButtonCompat">
         <item name="android:background">@drawable/button_borderless_compat</item>
     </style>
 
 </resources>