Tweak spacing for horizontal preferences.

- Add minHeight to horizontal preference so they are not clustered
together.
- Wrap app_data_usage's into different categories so they don't rely on
SpacePreference to draw space and dividers.

Change-Id: Ieed90a39d48494d1207680483968b5733bdfb344
Fix: 37750568
Test: visual

res/layout/horizontal_preference.xml

@@ -16,11 +16,12 @@
 -->
 
 
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
+    android:minHeight="?android:attr/listPreferredItemHeightSmall"
     android:orientation="horizontal"
-    android:paddingTop="1dp"
     android:paddingStart="@dimen/preference_no_icon_padding_start"
     android:paddingEnd="?android:attr/listPreferredItemPaddingEnd">
 

res/xml/app_data_usage.xml

@@ -20,8 +20,8 @@
     <com.android.settings.datausage.SpinnerPreference
         android:key="cycle" />
 
-    <com.android.settings.applications.SpacePreference
+    <PreferenceCategory
-        android:layout_height="8dp" />
+        android:key="app_data_usage_summary_category">
 
         <Preference
             android:key="total_usage"
@@ -41,9 +41,10 @@
             android:selectable="false"
             android:layout="@layout/horizontal_preference" />
 
-    <com.android.settings.applications.SpacePreference
+    </PreferenceCategory>
-        android:layout_height="8dp" />
 
+    <PreferenceCategory
+        android:key="app_data_usage_settings_category">
         <Preference
             android:key="app_settings"
             android:title="@string/data_usage_app_settings" />
@@ -58,6 +59,8 @@
             android:title="@string/unrestricted_app_title"
             android:summary="@string/unrestricted_app_summary" />
 
+    </PreferenceCategory>
+
     <PreferenceCategory
         android:key="app_list"
         android:title="@string/data_usage_other_apps" />