Search for runtime resource overlays in subdir.

See go/sku-colors. This changes the directory to search for framework
overlays if the right system property is defined. This allows
OEMs to specify different resources based on device SKUs.

Bug: 31692079
Change-Id: I9cb121b286b7f52aa26de1757fde1f3110cd47fd
diff --git a/include/androidfw/AssetManager.h b/include/androidfw/AssetManager.h
index 914ac3d..0b22802 100644
--- a/include/androidfw/AssetManager.h
+++ b/include/androidfw/AssetManager.h
@@ -72,6 +72,13 @@
     static const char* RESOURCES_FILENAME;
     static const char* IDMAP_BIN;
     static const char* OVERLAY_DIR;
+    /*
+     * If OVERLAY_SUBDIR_PROPERTY is set, search for runtime resource overlay
+     * APKs in OVERLAY_SUBDIR/<value of OVERLAY_SUBDIR_PROPERTY>/ rather than in
+     * OVERLAY_DIR.
+     */
+    static const char* OVERLAY_SUBDIR;
+    static const char* OVERLAY_SUBDIR_PROPERTY;
     static const char* TARGET_PACKAGE_NAME;
     static const char* TARGET_APK_PATH;
     static const char* IDMAP_DIR;