export libtonemap headers

libtonemap could be overridden by the vendor counterpart. The
headers should come from framework.

Bug: 200310159
Change-Id: I2685903543aac8c2d02fee2deba2c40dbb2f287c
diff --git a/libs/tonemap/tests/Android.bp b/libs/tonemap/tests/Android.bp
index f46f3fa..d519482 100644
--- a/libs/tonemap/tests/Android.bp
+++ b/libs/tonemap/tests/Android.bp
@@ -27,6 +27,9 @@
     srcs: [
         "tonemap_test.cpp",
     ],
+    header_libs: [
+        "libtonemap_headers",
+    ],
     shared_libs: [
         "android.hardware.graphics.common-V3-ndk",
     ],