SF: Flag guard setFrameRate() API

- LayerHistory is now always created
- Do not use LayerHistory when content detection flag is turned off.

Bug: 148428554
Test: atest CtsGraphicsTestCases:SetFrameRateTest
Test: Play YouTube video. When content detection flag is off,
      display runs at 90, otherwise at 60.
Test: adb shell /data/.../libsurfaceflinger_unittest
Change-Id: Iab8b79e16a5257c770d9ddd204cfe26d22de83b6
diff --git a/services/surfaceflinger/sysprop/api/SurfaceFlingerProperties-current.txt b/services/surfaceflinger/sysprop/api/SurfaceFlingerProperties-current.txt
index cdfd0f5..c66523a 100644
--- a/services/surfaceflinger/sysprop/api/SurfaceFlingerProperties-current.txt
+++ b/services/surfaceflinger/sysprop/api/SurfaceFlingerProperties-current.txt
@@ -121,6 +121,10 @@
     prop_name: "ro.surface_flinger.use_context_priority"
   }
   prop {
+    api_name: "use_frame_rate_api"
+    prop_name: "ro.surface_flinger.use_frame_rate_api"
+  }
+  prop {
     api_name: "use_smart_90_for_video"
     prop_name: "ro.surface_flinger.use_smart_90_for_video"
     deprecated: true