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/values/attrs.xml b/java/res/values/attrs.xml
index f03da4f..0e5b38b 100644
--- a/java/res/values/attrs.xml
+++ b/java/res/values/attrs.xml
@@ -15,11 +15,20 @@
 -->
 
 <resources>
+    <declare-styleable name="KeyboardTheme">
+        <!-- KeyboardView style -->
+        <attr name="keyboardViewStyle" format="reference" />
+        <attr name="keyPreviewStyle" format="reference" />
+        <!-- PopupMiniKeyboardView style -->
+        <attr name="popupMiniKeyboardViewStyle" format="reference" />
+        <attr name="popupMiniKeyboardPanelStyle" format="reference" />
+        <!-- Suggestions strip style -->
+        <attr name="suggestionsStripBackgroundStyle" format="reference" />
+        <attr name="suggestionBackgroundStyle" format="reference" />
+        <attr name="suggestionPreviewBackgroundStyle" format="reference" />
+    </declare-styleable>
 
     <declare-styleable name="KeyboardView">
-        <!-- Default KeyboardView style. -->
-        <attr name="keyboardViewStyle" format="reference" />
-
         <!-- Image for the key. This image needs to be a StateListDrawable, with the following
              possible states: normal, pressed, checkable, checkable+pressed, checkable+checked,
              checkable+checked+pressed. -->