Use Selector instead of Ripple on pre-L

Ripple was added in API level 21. We use Selector to respond to the
"press" event on older SDKs.

Bug: 25629359
Change-Id: Ie3a9ec09c45d4ed1534906a87db95ed372b75df9
diff --git a/res/drawable-v21/floating_action_button.xml b/res/drawable-v21/floating_action_button.xml
new file mode 100644
index 0000000..9a90112
--- /dev/null
+++ b/res/drawable-v21/floating_action_button.xml
@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+     Copyright (C) 2015 The Android Open Source Project
+
+     Licensed under the Apache License, Version 2.0 (the "License");
+     you may not use this file except in compliance with the License.
+     You may obtain a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+     Unless required by applicable law or agreed to in writing, software
+     distributed under the License is distributed on an "AS IS" BASIS,
+     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+     See the License for the specific language governing permissions and
+     limitations under the License.
+-->
+
+<ripple xmlns:android="http://schemas.android.com/apk/res/android"
+     android:color="@color/contacts_accent_color">
+     <item android:id="@android:id/mask">
+          <shape android:shape="oval">
+               <solid android:color="@android:color/white" />
+          </shape>
+     </item>
+</ripple>
\ No newline at end of file