Swap default_image from .png to .xml drawable

Save a few hundred KB in the APK

Change-Id: If212ac4af30f5a98f354ebd0820902269544f4ca
diff --git a/res/drawable/default_image.png b/res/drawable/default_image.png
deleted file mode 100644
index f6e6e60..0000000
--- a/res/drawable/default_image.png
+++ /dev/null
Binary files differ
diff --git a/res/drawable/default_image.xml b/res/drawable/default_image.xml
new file mode 100644
index 0000000..0a4369a
--- /dev/null
+++ b/res/drawable/default_image.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+       android:shape="rectangle">
+
+  <!-- these are the dimensions of the original default_image.png -->
+  <size
+      android:width="215dp"
+      android:height="210dp" />
+
+  <solid
+      android:color="#ccc" />
+
+</shape>
\ No newline at end of file