change tab focus highlight

       Two px wide green stroke added for tab focus highlight.

Change-Id: I77fc9e20414e4bad593bf76b5aab6e19f3f1ff74
diff --git a/res/values/dimensions.xml b/res/values/dimensions.xml
index d0552a0..3badd17 100644
--- a/res/values/dimensions.xml
+++ b/res/values/dimensions.xml
@@ -20,6 +20,7 @@
     <dimen name="tab_overlap">8dp</dimen>
     <dimen name="tab_addoverlap">14dp</dimen>
     <dimen name="tab_slice">15.5dp</dimen>
+    <dimen name="tab_focus_stroke">2dip</dimen>
     <dimen name="max_tab_width">300dp</dimen>
     <dimen name="bookmarkThumbnailWidth">90dip</dimen>
     <dimen name="bookmarkThumbnailHeight">80dip</dimen>