Multi-user and WallpaperColors

Test: set different wallpapers for different users and switch between them.
Test: re-ran cts tests at cts/tests/app/src/android/app/cts/WallpaperManagerTest.java
Change-Id: Ic06d1dc6db26869a2948590863ca9b8ac81c630e
Fixes: 63513694
diff --git a/core/java/android/app/WallpaperColors.java b/core/java/android/app/WallpaperColors.java
index d0791cf..2a8130f 100644
--- a/core/java/android/app/WallpaperColors.java
+++ b/core/java/android/app/WallpaperColors.java
@@ -408,4 +408,13 @@
 
         return new Size(newWidth, newHeight);
     }
+
+    @Override
+    public String toString() {
+        final StringBuilder colors = new StringBuilder();
+        for (int i = 0; i < mMainColors.size(); i++) {
+            colors.append(Integer.toHexString(mMainColors.get(i).toArgb())).append(" ");
+        }
+        return "[WallpaperColors: " + colors.toString() + "h: " + mColorHints + "]";
+    }
 }