Support invalidating multiple keys in KeyboardView

Change-Id: I347ccfc2cf60c17f5f0eddec6566662cb3a954ca
diff --git a/java/res/values/attrs.xml b/java/res/values/attrs.xml
index d4a50b6..219e327 100644
--- a/java/res/values/attrs.xml
+++ b/java/res/values/attrs.xml
@@ -114,7 +114,7 @@
 
         <attr name="shadowColor" format="color" />
         <attr name="shadowRadius" format="float" />
-        <attr name="backgroundDimAmount" format="float" />
+        <attr name="backgroundDimAlpha" format="integer" />
 
         <attr name="keyTextStyle" format="enum">
             <!-- This should be aligned with Typeface.NORMAL etc. -->