Use custom theme for Keyboard theme switch

This change reduces the number of layout files and make these
theme-generic.  This might be very helpful to re-design suggestion
strip.

Bug: 4175031
Change-Id: Idca10a4aa0bf7ac496eedd1879311e59780a423b
diff --git a/java/res/layout-xlarge/candidates.xml b/java/res/layout-xlarge/candidates.xml
index e111acd..93b0304 100644
--- a/java/res/layout-xlarge/candidates.xml
+++ b/java/res/layout-xlarge/candidates.xml
@@ -34,9 +34,9 @@
         android:orientation="horizontal"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:background="@drawable/keyboard_suggest_strip_holo"
         android:paddingRight="@dimen/candidate_strip_padding"
         android:paddingLeft="@dimen/candidate_strip_padding"
+        style="?attr/suggestionsStripBackgroundStyle"
     >
         <HorizontalScrollView
             android:layout_width="match_parent"