Set track drawable to null to remove grey track.

Bug: 18933278
Change-Id: I8e5a13ac53320967c34feaf20f24348be14c9216
diff --git a/res/values/styles.xml b/res/values/styles.xml
index 06f1afe..d4826a1 100644
--- a/res/values/styles.xml
+++ b/res/values/styles.xml
@@ -62,6 +62,7 @@
         <item name="android:actionOverflowButtonStyle">@style/ContactsActionBarOverflowQP</item>
         <item name="android:actionModeCloseDrawable">@drawable/ic_close_lt</item>
         <item name="android:fastScrollThumbDrawable">@drawable/fastscroll_thumb</item>
+        <item name="android:fastScrollTrackDrawable">@null</item>
         <item name="android:textColorPrimary">@color/primary_text_color</item>
         <item name="android:textColorSecondary">@color/secondary_text_color</item>
         <item name="android:icon">@android:color/transparent</item>