Add wallpaper zoom to areas that have blur

Whenever blurring, the wallpaper should also zoom out. This is the
mental model of our Depth System.

Test: manual
Bug: 149792636
Change-Id: I1783eb87fefeb6f917f0ba64f2c6ec8f1f2004fa
diff --git a/src/com/android/launcher3/LauncherState.java b/src/com/android/launcher3/LauncherState.java
index df71f16..6ee82cd 100644
--- a/src/com/android/launcher3/LauncherState.java
+++ b/src/com/android/launcher3/LauncherState.java
@@ -271,11 +271,13 @@
     }
 
     /**
-     * The amount of blur to apply to the background of either the app or Launcher surface in this
-     * state.
+     * The amount of blur and wallpaper zoom to apply to the background of either the app
+     * or Launcher surface in this state. Should be a number between 0 and 1, inclusive.
+     *
+     * 0 means completely zoomed in, without blurs. 1 is zoomed out, with blurs.
      */
-    public int getBackgroundBlurRadius(Context context) {
-        return 0;
+    public float getDepth(Context context) {
+        return 0f;
     }
 
     public String getDescription(Launcher launcher) {