Fix incorrect colored bar when task bar is hidden

Set backgorund color on content id view instead of homepage view.
Also setup edge to edge for the homepage.

Fix: 215440529
Test: See correct ui on the two pane mode and regular phone.
Change-Id: I2d5988a489410e9620137bd6cf9607768787d4fc

res/layout/settings_homepage_container.xml

@@ -19,7 +19,6 @@
     xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:app="http://schemas.android.com/apk/res-auto"
     android:id="@+id/settings_homepage_container"
-    android:fitsSystemWindows="true"
     android:layout_width="match_parent"
     android:layout_height="match_parent">