Revert "Revert "SurfaceFlinger: add a sysprop for GL backpressure""

This reverts commit cc1ce6476e4deb8877c10b2a59afd27556ec72e9.

Reason for revert: This change is needed to fix b/138083790. The underlying issue causing the first revert is now resolved.

Change-Id: I82eeec5f5e66570e03f37294d7bbe15c41fec86e
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index ddfe88c..5265594 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -1003,6 +1003,7 @@
     volatile nsecs_t mDebugInTransaction = 0;
     bool mForceFullDamage = false;
     bool mPropagateBackpressure = true;
+    bool mPropagateBackpressureClientComposition = false;
     std::unique_ptr<SurfaceInterceptor> mInterceptor;
     SurfaceTracing mTracing{*this};
     bool mTracingEnabled = false;