Default icon should match platform one even on N and below devices.
Bug: 63083094

Change-Id: Ie08ccaf63a49fa766f0d51d840d7763fc4bf2a5a
diff --git a/src/com/android/launcher3/IconCache.java b/src/com/android/launcher3/IconCache.java
index a23a674..4b71ba0 100644
--- a/src/com/android/launcher3/IconCache.java
+++ b/src/com/android/launcher3/IconCache.java
@@ -120,7 +120,8 @@
     }
 
     private Drawable getFullResDefaultActivityIcon() {
-        return getFullResIcon(Resources.getSystem(), android.R.drawable.sym_def_app_icon);
+        return getFullResIcon(Resources.getSystem(), Utilities.isAtLeastO() ?
+                android.R.drawable.sym_def_app_icon : android.R.mipmap.sym_def_app_icon);
     }
 
     private Drawable getFullResIcon(Resources resources, int iconId) {