Run the CtsGraphicsTestCases in presubmit for libpng.

Bug: https://issuetracker.google.com/135180511
Test: treehugger
Change-Id: I3d545db6eabcb25eaf3aad4f5e58877db2e0162e
diff --git a/TEST_MAPPING b/TEST_MAPPING
new file mode 100644
index 0000000..10bd0ee
--- /dev/null
+++ b/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "CtsGraphicsTestCases"
+    }
+  ]
+}