Special handling of one key mini-keyboard to mitigate visual flicker

Use pre-computed width and height of mini keyboard if
 * Popup key preview is enabled
 * The mini keyboard has only one key
 * Pre-computed width and height are specified

Bug: 5248783
Change-Id: I53475698e87d5bd67d36e63323c25a9e9f18fbb1
diff --git a/java/res/values/styles.xml b/java/res/values/styles.xml
index 30c0e5a..43aa583 100644
--- a/java/res/values/styles.xml
+++ b/java/res/values/styles.xml
@@ -259,6 +259,8 @@
         <item name="keyPreviewBackground">@drawable/keyboard_key_feedback_ics</item>
         <item name="keyPreviewLeftBackground">@drawable/keyboard_key_feedback_left_ics</item>
         <item name="keyPreviewRightBackground">@drawable/keyboard_key_feedback_right_ics</item>
+        <item name="keyPreviewBackgroundWidth">@dimen/keyboard_key_feedback_background_holo_width</item>
+        <item name="keyPreviewBackgroundHeight">@dimen/keyboard_key_feedback_background_holo_height</item>
         <item name="keyPreviewTextColor">#FFFFFFFF</item>
         <item name="keyPreviewHeight">@dimen/key_preview_height_ics</item>
         <item name="keyPreviewOffset">@dimen/key_preview_offset_ics</item>