Use slightly dimmed text color for functional keys

This CL introduces two new key attributes to achieve this.
- KeyboardView.functionalTextColor
- followFunctionalTextColor flag for Key.keyLabelFlags

Bug: 14419121
Change-Id: I45ca433dcc9cc8c6cf891e21d5316ee4048b0cad
diff --git a/java/res/values/themes-ics.xml b/java/res/values/themes-ics.xml
index 560cfc5..79f9036 100644
--- a/java/res/values/themes-ics.xml
+++ b/java/res/values/themes-ics.xml
@@ -53,6 +53,7 @@
         <item name="keyTypeface">bold</item>
         <item name="keyTextColor">@color/key_text_color_holo</item>
         <item name="keyTextInactivatedColor">@color/key_text_inactivated_color_holo</item>
+        <item name="functionalTextColor">@color/key_text_color_holo</item>
         <item name="keyHintLetterColor">@color/key_hint_letter_color_holo</item>
         <item name="keyHintLabelColor">@color/key_hint_label_color_holo</item>
         <item name="keyShiftedLetterHintInactivatedColor">@color/key_shifted_letter_hint_inactivated_color_holo</item>