Add keyboard shadow

This CL sets 8dp elevation ot input view in order to cast a shadow
onto underlying application.

Bug: 16210054
Change-Id: I7779c63612fc88e24dde65de3e4e7a45b9d1762f
diff --git a/java/res/values/attrs.xml b/java/res/values/attrs.xml
index f2072fd..be35d13 100644
--- a/java/res/values/attrs.xml
+++ b/java/res/values/attrs.xml
@@ -20,6 +20,8 @@
 
 <resources>
     <declare-styleable name="KeyboardTheme">
+        <!-- InputView style -->
+        <attr name="inputViewStyle" format="reference" />
         <!-- Keyboard style -->
         <attr name="keyboardStyle" format="reference" />
         <!-- KeyboardView style -->