SF: Set up libscheduler headers

Start pulling Scheduler sources into a libscheduler target akin to
librenderengine and libcompositionengine.

Bug: 185535769
Test: Build
Change-Id: I8ee871cce96209c8c53601152501129b09c5e46f
diff --git a/services/surfaceflinger/FrameTimeline/Android.bp b/services/surfaceflinger/FrameTimeline/Android.bp
index 10a5833..2d4ec04 100644
--- a/services/surfaceflinger/FrameTimeline/Android.bp
+++ b/services/surfaceflinger/FrameTimeline/Android.bp
@@ -13,6 +13,9 @@
     srcs: [
         "FrameTimeline.cpp",
     ],
+    header_libs: [
+        "libscheduler_headers",
+    ],
     shared_libs: [
         "android.hardware.graphics.composer@2.4",
         "libbase",