Updating the default widget preview generation logic

We draw a while round rect box which is divided into the cells to
represent the widget size. The app icon is drawn in the center
for this white box.

Bug: 34819119
Change-Id: Ie4d83712577f21b276c6744a55993f71da368398
diff --git a/res/values/dimens.xml b/res/values/dimens.xml
index 2cf17ea..9c8162b 100644
--- a/res/values/dimens.xml
+++ b/res/values/dimens.xml
@@ -85,6 +85,11 @@
     <dimen name="widget_preview_label_vertical_padding">8dp</dimen>
     <dimen name="widget_preview_label_horizontal_padding">16dp</dimen>
 
+    <dimen name="widget_preview_shadow_blur">0.5dp</dimen>
+    <dimen name="widget_preview_key_shadow_distance">1dp</dimen>
+    <dimen name="widget_preview_corner_radius">2dp</dimen>
+    <dimen name="widget_preview_cell_divider_width">0.5dp</dimen>
+
     <dimen name="widget_section_height">56dp</dimen>
     <dimen name="widget_section_icon_size">40dp</dimen>
     <dimen name="widget_section_vertical_padding">8dp</dimen>