Improve layers debugging

Change-Id: Ia4950dd5f0e0a224ecb69c581d33aa4f32260a7c
diff --git a/libs/hwui/LayerCache.h b/libs/hwui/LayerCache.h
index 81b8bf3..a0eae59 100644
--- a/libs/hwui/LayerCache.h
+++ b/libs/hwui/LayerCache.h
@@ -101,6 +101,11 @@
      */
     uint32_t getSize();
 
+    /**
+     * Prints out the content of the cache.
+     */
+    void dump();
+
 private:
     void deleteLayer(Layer* layer);