Always enable backpressure propagation during GPU composition

Change I54f1bd6074e27fb6e00d8397a704fc1d5f1ddd35 relaxed the condition
enabling backpressure propagation to be in all cases where device
composition was performed. This change re-tightens that condition so
that propagation is never enabled when GPU composition is performed.

Bug: 131134223
Test: systrace
Change-Id: If89aae62dc362ca0e471439a26c211acca5184f1
diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index fc0d5fc..bac5bf0 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -1632,7 +1632,7 @@
             }
 
             // For now, only propagate backpressure when missing a hwc frame.
-            if (hwcFrameMissed) {
+            if (hwcFrameMissed && !gpuFrameMissed) {
                 if (mPropagateBackpressure) {
                     signalLayerUpdate();
                     break;