Add minTickWidth for the bar chart

At jsharkey's request.

Change-Id: Ic489e534fe793fc7ec3fd2bedc5bb256be99daec

res/layout/preference_memoryusage.xml

@@ -16,6 +16,7 @@
 
 <com.android.settings.deviceinfo.PercentageBarChart
         xmlns:android="http://schemas.android.com/apk/res/android"
+        xmlns:settings="http://schemas.android.com/apk/res/com.android.settings"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:minHeight="?android:attr/listPreferredItemHeight"
@@ -24,5 +25,6 @@
         android:paddingRight="?android:attr/scrollbarSize"
         android:paddingTop="6dip"
         android:paddingBottom="6dip"
-        emptyColor="@color/memory_avail">
-</com.android.settings.deviceinfo.PercentageBarChart>
+        settings:minTickWidth="6dip"
+        settings:emptyColor="@color/memory_avail">
+</com.android.settings.deviceinfo.PercentageBarChart>

res/values/attrs.xml

@@ -46,5 +46,7 @@
     <declare-styleable name="PercentageBarChart">
         <!-- Background color -->
         <attr name="emptyColor" format="color" />
+        <!-- Minimum tick width for each slice in the bar chart. -->
+        <attr name="minTickWidth" format="dimension" />
     </declare-styleable>
 </resources>