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/renderengine/Android.bp b/libs/renderengine/Android.bp
index 07c5dd8..84e84dd 100644
--- a/libs/renderengine/Android.bp
+++ b/libs/renderengine/Android.bp
@@ -122,6 +122,9 @@
         ":librenderengine_threaded_sources",
         ":librenderengine_skia_sources",
     ],
+    header_libs: [
+        "libtonemap_headers",
+    ],
     include_dirs: [
         "external/skia/src/gpu",
     ],