Update layout make talkback first focus item is root button

Because chips layout parent is higher than tool bar, talkback
will focus on that layout child which is chip firstly. Change
layout parent space to margin let tool bar layout is highest
layout in this layer to fix this bug.

Fix: 124342125
Test: manual
Test: atest DocumentsUIGoogleTests
Change-Id: I1692b24a9ea305b4ea13db024b66e7d1f29039c9
diff --git a/res/values/dimens.xml b/res/values/dimens.xml
index 6d9f7b3..60ab9f0 100644
--- a/res/values/dimens.xml
+++ b/res/values/dimens.xml
@@ -115,6 +115,7 @@
     <dimen name="action_bar_size">48dp</dimen>
     <!--This value should equal actionBarSize + (2 x search_bar_margin)-->
     <dimen name="action_bar_space_height">64dp</dimen>
+    <dimen name="action_bar_space_margin">@dimen/action_bar_space_height</dimen>
 
     <dimen name="refresh_icon_range">64dp</dimen>
 </resources>