Notifications custom layouts: make the buttons look good in Material.

* Tweak the spacing to be identical to the standard layout
* Tweak the ripple to look good

BUG=541617

Review URL: https://codereview.chromium.org/1418813010

Cr-Commit-Position: refs/heads/master@{#357074}

chrome/android/java/res/drawable-v21/web_notification_button_background.xml

+<?xml version="1.0" encoding="utf-8"?>
+<!-- Copyright 2015 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. -->
+
+<ripple xmlns:android="http://schemas.android.com/apk/res/android"
+    android:color="@color/ripple_material_light">
+    <item android:id="@android:id/mask"
+          android:drawable="@drawable/button_compat_shape" />
+</ripple>

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

@@ -81,7 +81,7 @@
             style="@style/WebNotificationDivider"
             android:layout_width="match_parent"
             android:layout_height="1dp"
-            android:layout_marginBottom="8dp"
+            android:layout_marginTop="2dp"
             android:contentDescription="@null"
             android:visibility="gone"/>
 
@@ -89,8 +89,8 @@
             android:id="@+id/buttons"
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
+            android:layout_marginStart="-8dp"
             android:orientation="horizontal"        
-            android:layout_marginBottom="8dp"
             android:visibility="gone"/>
 
         <ImageView

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

@@ -9,9 +9,9 @@
     android:gravity="start|center_vertical"
     android:id="@+id/button"
     android:layout_height="48dp"
-    android:layout_marginEnd="8dp"
     android:layout_weight="1"
     android:layout_width="0dp"
+    android:paddingStart="8dp"
     android:singleLine="true"
     android:textSize="13sp"
     style="@style/WebNotificationButton"/>

chrome/android/java/res/values-v21/styles.xml

@@ -78,8 +78,8 @@
     </style>
     <style name="WebNotificationButton"
         parent="@android:style/Widget.DeviceDefault.Light.Button.Borderless.Small">
-        <!-- From the non-public Color secondary_text_default_material_light -->
-        <item name="android:textColor">#8a000000</item>
+        <item name="android:textColor">@color/secondary_text_default_material_light</item>
+        <item name="android:background">@drawable/web_notification_button_background</item>
     </style>
 
     <style name="IncognitoTheme" parent="MainTheme">