Align root icons with the action bar icon.

Change-Id: I37ac445a562aaba55496adcf7cbf1768236bf7c0
diff --git a/res/values/dimens.xml b/res/values/dimens.xml
index fb793a2..f94a00e 100644
--- a/res/values/dimens.xml
+++ b/res/values/dimens.xml
@@ -17,6 +17,7 @@
 <resources>
     <dimen name="icon_size">40dp</dimen>
     <dimen name="root_icon_size">24dp</dimen>
+    <dimen name="root_icon_margin">0dp</dimen>
 
     <dimen name="grid_width">152dp</dimen>
     <dimen name="grid_height">176dp</dimen>