Separate functional key background from normal one

This CL also moves spacebarBackground attribute from MainKeyboardView
to KeyboardView.

This CL must be checked in together with I48c383ca97.

Bug: 14419121
Change-Id: Id356d0086a8fb21375fb5c66076873258fb3d63e
diff --git a/java/res/values/themes-common.xml b/java/res/values/themes-common.xml
index 76abb10..df26fb3 100644
--- a/java/res/values/themes-common.xml
+++ b/java/res/values/themes-common.xml
@@ -109,12 +109,7 @@
     <style name="KeyPreviewTextView" />
     <!-- Though {@link EmojiPalettesView} doesn't extend {@link KeyboardView}, some views inside it,
          for instance delete button, need themed {@link KeyboardView} attributes. -->
-    <style
-        name="EmojiPalettesView"
-        parent="KeyboardView"
-    >
-        <item name="emojiTabLabelColor">@color/emoji_tab_label_color_holo</item>
-    </style>
+    <style name="EmojiPalettesView" />
     <style name="MoreKeysKeyboard" />
     <style
         name="MoreKeysKeyboardView"