[SF] Extract {Display|Layer}RenderArea to separate files

This CL also fixes incorrect sampling bounds in RegionSamplingThread,
caused by ag/11837111.

Bug: 158599281
Test: atest libsurfaceflinger_unittest
Test: take a screenshot from launcher
Test: take a screenshot from YouTube while playing a video
Change-Id: I7e7777071e91a833a7bad4bd77e9d0c989fea9b7
diff --git a/services/surfaceflinger/Android.bp b/services/surfaceflinger/Android.bp
index a790d0b..804a3c3 100644
--- a/services/surfaceflinger/Android.bp
+++ b/services/surfaceflinger/Android.bp
@@ -145,6 +145,7 @@
         "DisplayHardware/HWComposer.cpp",
         "DisplayHardware/PowerAdvisor.cpp",
         "DisplayHardware/VirtualDisplaySurface.cpp",
+        "DisplayRenderArea.cpp",
         "Effects/Daltonizer.cpp",
         "EventLog/EventLog.cpp",
         "FrameTracer/FrameTracer.cpp",
@@ -152,6 +153,7 @@
         "Layer.cpp",
         "LayerProtoHelper.cpp",
         "LayerRejecter.cpp",
+        "LayerRenderArea.cpp",
         "LayerVector.cpp",
         "MonitoredProducer.cpp",
         "NativeWindowSurface.cpp",