the scroll drag area was too small, and should have come from a resource anyway.

Change-Id: I11111aff767e21a2582c5c368b5d9ff1ac8f9cd7
diff --git a/res/values/dimens.xml b/res/values/dimens.xml
index 790f835..c83986b 100644
--- a/res/values/dimens.xml
+++ b/res/values/dimens.xml
@@ -37,4 +37,8 @@
     
     <!-- delete_zone_size_full - button_bar_height_portrait -->
     <dimen name="delete_zone_padding">14dip</dimen>
+
+    <!-- the area at the edge of the screen that makes the workspace go left
+         or right while you're dragging. -->
+    <dimen name="scroll_zone">20dp</dimen>
 </resources>