Add loaders to DrawerFragment and make status bar transparent

- This CL addresses a TODO to load groups and filters from
  DrawerFragment directly.
- Also, avoiding adding fragments to FragmentManager of a
  Fragment works around a crash on LMP.
- Wrap RecyclerView with a FrameLayout to go full screen
  with a ScrimDrawable

Bug: 34062530

Test: add and remove accounts and observe changes in side nav

Change-Id: I63943a9d596aa32301609d6ab1b9d49c0c784356
diff --git a/res/layout/drawer_fragment.xml b/res/layout/drawer_fragment.xml
index ea9eed0..eeb792e 100644
--- a/res/layout/drawer_fragment.xml
+++ b/res/layout/drawer_fragment.xml
@@ -15,15 +15,18 @@
      limitations under the License.
 -->
 
+<!-- Layout for the navigation drawer. The content view needs to be wrapped in a FrameLayout in
+     order to go full screen with a ScrimDrawable. -->
 <FrameLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/drawer_fragment_root"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:fitsSystemWindows="true">
 
     <android.support.v7.widget.RecyclerView
         android:id="@+id/list"
-        android:background="#FAFAFA"
+        android:background="@color/navigation_drawer_background_color"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
         android:divider="@null" />